Wideband Energy Harvesting Device Integrated with Sensors Inside Automotive Tires and Its Design Method

Abstract

The present invention discloses a broadband energy harvesting device integrated with a sensor inside an automobile tire and its design method. The broadband energy harvesting device includes a broadband energy harvesting device body and an LTC3588-1 chip. The output end of the broadband energy harvesting device body is respectively connected to the PZ1 and PZ2 pins of the LTC3588-1 chip. The broadband energy harvesting device body includes a first fixing frame, a coil, and a permanent magnet core. An elastic thin sheet is fixedly arranged at the top of the first fixing frame, and a piezoelectric ceramic sheet is arranged on the elastic thin sheet. The permanent magnet core is located inside the coil, constraint springs are arranged at both ends of the permanent magnet core, and a counterweight is arranged at the suspended end of the elastic thin sheet. The broadband energy harvesting device in the present invention can improve the utilization rate of converting mechanical energy into electrical energy and can reach the voltage stabilization threshold of the circuit within a wider speed range.

Description

Technical Field

[0001] The present invention relates to the technical field of broadband energy harvesting devices, and particularly to a broadband energy harvesting device integrated with sensors inside an automotive tire and a design method thereof. Background Art

[0002] With the development of industrial level and science and technology, China's automotive manufacturing industry has continuously broken through new technologies. Although it lags behind some industrial powers in some traditional processes, China has firmly grasped the development trend of new energy vehicles and belongs to the first echelon in the intelligent automotive production design. When it comes to intelligent vehicles, intelligent tires are indispensable. Integrating various types of sensors in the tires can directly reflect information such as tire pressure and temperature to the driver, which not only provides convenience for the driver but also improves driving safety. In the prior art, almost all power supplies for sensors use batteries, but batteries have many disadvantages:

[0003] (1) Lifespan limitation. Commercially available lithium batteries generally have strict charge and discharge times. Generally, after three to five years, the battery's storage capacity and performance cannot be guaranteed. Moreover, since the sensors are arranged inside the wheel hub, replacing the battery is also a troublesome task.

[0004] (2) High requirements for the working environment. The working environment has a great impact on the battery's working state. High and low temperatures, high pressures, and severe vibrations, etc., may damage the battery or even directly render it useless, while the working environment of tires is often very complex.

[0005] (3) Recycling and treatment problems. Recycling of waste batteries has always been a difficult issue. Since batteries contain a large amount of heavy metals, their recycling and degradation are very difficult to achieve. Summary of the Invention

[0006] Aiming at the above existing problems, the present invention aims to provide a broadband energy harvesting device integrated with sensors inside an automotive tire and a design method thereof, which can reach the voltage stabilization threshold of the circuit within a wider speed range.

[0007] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0008] A broadband energy harvesting device integrated with sensors inside an automotive tire, including a broadband energy harvesting device body, characterized in that: the broadband energy harvesting device body includes a first fixing frame, a coil, and a permanent magnet core. An elastic thin sheet is fixedly provided at the top of the first fixing frame. One end of the elastic thin sheet is fixedly connected to the first fixing frame, and the other end of the elastic thin sheet is suspended, and a piezoelectric ceramic sheet is provided on the elastic thin sheet;

[0009] The coil is cylindrical, the permanent magnet core is cylindrical in structure, and the permanent magnet core is located inside the coil. One end of the coil is connected to the first fixing bracket, and the other end of the coil is connected to a second fixing bracket. The first fixing bracket and the second fixing bracket are arranged in parallel;

[0010] The wide - band energy - capturing device body further includes a leveling component for adjusting the power generation effect of the device.

[0011] Furthermore, the leveling component includes restraint springs fixed at both ends of the permanent magnet core. The ends of the two restraint springs away from the permanent magnet core are respectively connected to the corresponding first fixing bracket or the second fixing bracket.

[0012] Furthermore, the length of the restraint spring is 50 mm and the wire diameter is 0.4 mm.

[0013] Furthermore, the leveling component further includes a counterweight detachably connected to the elastic thin sheet. The counterweight is located at the end of the elastic thin sheet away from the first fixing bracket.

[0014] Furthermore, the wide - band energy - capturing device further includes an LTC3588 - 1 chip. The output end of the wide - band energy - capturing device body is respectively connected to the PZ1 and PZ2 pins of the LTC3588 - 1 chip.

[0015] Furthermore, a design method for a wide - band energy - capturing device integrated with sensors inside an automobile tire is characterized by including the following steps,

[0016] S1: Design the structure of the wide - band energy - capturing device body;

[0017] S2: Design an energy - harvesting circuit, select a chip, and connect it to the wide - band energy - capturing device body to form a complete wide - band energy - capturing device;

[0018] S3: Conduct piezoelectric experimental platform tests on the piezoelectric ceramic sheets used in the wide - band energy - capturing device body in step S1;

[0019] S4: Conduct in - vehicle piezoelectric tests on the piezoelectric ceramic sheets used in the wide - band energy - capturing device body in step S1, and add a counterweight to the elastic thin sheet;

[0020] S5: Conduct electromagnetic power - generation experiments on the coil and the permanent magnet core used in the wide - band energy - capturing device body in step S1, and install restraint springs at both ends of the permanent magnet core.

[0021] Furthermore, the specific operations of step S4 include the following steps,

[0022] S401: Install the piezoelectric ceramic sheets used in the wide - band energy - capturing device body at the position of the automobile wheel hub;

[0023] S402: Connect the piezoelectric ceramic sheet to the oscilloscope using a conductive slip ring;

[0024] S403: Drive at different speeds on different road surfaces and observe the waveform of the oscilloscope.

[0025] Furthermore, the specific operations of step S5 include the following steps,

[0026] S501: Conduct electromagnetic power generation experiments on the coils and permanent magnet cores used in the broadband energy harvesting device body;

[0027] S502: Calculate the voltage output from the broadband energy harvesting device to both ends of the load according to the principle of full-bridge rectification-capacitor filtering circuit;

[0028] S503: Install constraint springs at both ends of the permanent magnet core and adjust the length and wire diameter of the constraint springs according to the voltage at both ends of the load in step S502.

[0029] Furthermore, the specific operations of step S502 include the following steps,

[0030] Let the load voltage V L Remain constant. During the change period of the input voltage curve [t1, t3], due to the law of conservation of charge, the total amount of input charge is equal to the sum of the charge output to the load and the charge flowing through the capacitor C r Because the load voltage V L Is stable, so

[0031]

[0032] In the formula, R L Is the equivalent load resistance; T is the modulation signal period; I is the circuit current;

[0033] Calculating the above formula gives

[0034]

[0035] In the formula, U M Represents the amplitude of the vibration displacement; α represents the piezoelectric stress factor; C1 represents the equivalent capacitance of the piezoelectric sheet; ω is the vibration angular frequency;

[0036] Then the load voltage is expressed as

[0037]

[0038] From the above formula, the collection power of the circuit is

[0039]

[0040] Let:

[0041]

[0042] The optimal output load is

[0043]

[0044] The maximum output power is

[0045]

[0046] At this time, the voltage across the load is

[0047]

[0048] The beneficial effects of the present invention are:

[0049] The broadband energy capture device disclosed in the present invention uses a combination of piezoelectric effect power generation and electromagnetic induction power generation to generate electricity, which can improve the utilization rate of mechanical energy converted into electrical energy. At the same time, according to the relationship between the circuit output load and the output power and the load, constraint springs are installed at both ends of the permanent magnet core, and a counterweight screw is added at the end that is elastically away from the first fixed frame, thereby further improving the power generation efficiency and being able to reach the circuit voltage stability threshold within a wider speed range. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the main structure of the broadband energy harvesting device in Example 1 of the present invention.

[0051] Figure 2 This is a connection diagram of a full-wave bridge rectifier circuit in the second embodiment of the present invention.

[0052] Figure 3 This is a connection diagram of a full-wave bridge rectifier-capacitor filter circuit in the second embodiment of the present invention.

[0053] Figure 4 This is an input-output waveform diagram of the full-wave bridge rectifier-capacitor filter circuit in Example 2 of the present invention.

[0054] Figure 5 This is the internal logic diagram of the LTC3588-1 in Example 2 of the present invention.

[0055] Figure 6 This is a connection diagram between the energy harvesting circuit and the energy harvesting device in the second embodiment of the present invention.

[0056] Figure 7 This is a diagram of the piezoelectric experimental platform for piezoelectric ceramic sheets in Example 2 of the present invention.

[0057] Figure 8 This is a waveform diagram of the piezoelectric experiment output of the piezoelectric ceramic piece in Example 2 of the present invention.

[0058] Figure 9 It is the frequency-maximum voltage graph of the piezoelectric ceramic sheet under different vibration intensities in the second embodiment of the present invention.

[0059] Figure 10 It is the output waveform graph of the piezoelectric test of the piezoelectric ceramic sheet on a real vehicle in the second embodiment of the present invention.

[0060] Figure 11 It is a schematic diagram of different flatness road surfaces used in the piezoelectric test of the piezoelectric ceramic sheet on a real vehicle in the second embodiment of the present invention.

[0061] Figure 12 It is the output of the piezoelectric power generation of the piezoelectric ceramic sheet on a real vehicle after voltage stabilization in the second embodiment of the present invention.

[0062] Figure 13 It is the output waveform graph of the power generation experiment of the coil and the permanent magnet core in the second embodiment of the present invention.

[0063] Figure 14 It is the overall circuit simulation diagram of the energy harvesting circuit based on the LTC3588-1 chip in the third embodiment of the present invention.

[0064] Figure 15 It is the input-output simulation waveform graph of the overall circuit in the third embodiment of the present invention.

[0065] Figure 16 It is the overall circuit PCB design diagram of the energy harvesting circuit based on the LTC3588-1 chip in the third embodiment of the present invention.

[0066] Figure 17 It is the physical entity of the overall circuit PCB board of the energy harvesting circuit based on the LTC3588-1 chip in the third embodiment of the present invention.

[0067] Wherein: 1 - first fixing frame, 2 - coil, 3 - permanent magnet core, 4 - elastic thin sheet, 5 - piezoelectric ceramic sheet, 6 - second fixing frame, 7 - constraint spring, 8 - counterweight. Detailed implementation manners

[0068] In order to enable those of ordinary skill in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the drawings and embodiments.

[0069] Embodiment 1:

[0070] A broadband energy harvesting device integrated with sensors inside an automotive tire includes a broadband energy harvesting device body and an LTC3588-1 chip. The output ends of the broadband energy harvesting device body are respectively connected to the PZ1 and PZ2 pins of the LTC3588-1 chip.

[0071] The broadband energy harvesting device body is as shown in the appendixFigure 1 As shown in the figure, it includes a first fixing frame 1, a coil 2, and a permanent magnet core 3. An elastic thin sheet 4 is fixedly arranged on the top of the first fixing frame 1. One end of the elastic thin sheet 4 is fixedly connected to the first fixing frame 1, and the other end of the elastic thin sheet 4 is suspended. A piezoelectric ceramic sheet 5 is arranged on the elastic thin sheet 4;

[0072] The coil 2 is wound into a cylindrical shape. The permanent magnet core 3 is of a cylindrical structure, and the permanent magnet core 3 is located inside the coil 2. One end of the coil 2 is connected to the first fixing frame 1, and the other end of the coil 2 is connected to a second fixing frame 6. The first fixing frame 1 and the second fixing frame 6 are arranged in parallel;

[0073] The wide - band energy - harvesting device body further includes a leveling component for adjusting the power generation effect of the device; the leveling component includes constraint springs 7 fixedly arranged at both ends of the permanent magnet core 3. The ends of the two constraint springs 7 far from the permanent magnet core 3 are respectively connected to the corresponding first fixing frame 1 or second fixing frame 6.

[0074] The leveling component further includes a counterweight 8 detachably connected to the elastic thin sheet 4. The counterweight 8 is located at the end of the elastic thin sheet 4 far from the first fixing frame 1.

[0075] Preferably, the length of the constraint spring 7 is 50 mm, and the wire diameter is 0.4 mm.

[0076] Embodiment Two:

[0077] Embodiment Two is a design method for the wide - band energy - harvesting device for an integrated sensor inside an automobile tire described in Embodiment One, including the following steps,

[0078] S1: Design the structure of the wide - band energy - harvesting device body as described in Embodiment One;

[0079] S2: Design an energy - harvesting circuit, select a chip, and connect it to the wide - band energy - harvesting device body to form a complete wide - band energy - harvesting device;

[0080] Specifically, due to complex working conditions, poor material stability, and irregular movement of the device itself, etc., there are large fluctuations in the voltage directly output by the energy - harvesting device. To make the generated electrical energy can be effectively utilized, it needs to be converted into a low - voltage DC output that the sensor can use through an energy - harvesting circuit. The basic function required by the energy - harvesting circuit is rectification and filtering.

[0081] The function of the rectifier circuit is to convert AC electrical energy into DC electrical energy. To convert an AC signal into DC, the unidirectional conduction characteristic of diodes needs to be utilized. There are many forms of basic rectifier circuits, and four of them are widely used, namely half-wave rectification, full-wave rectification, full-wave bridge rectification, and voltage multiplier rectification circuits. In this application, the full-wave bridge rectification circuit is selected as the rectifier circuit, and its connection method is as shown in the appendix Figure 2 as shown.

[0082] The function of filtering is to select the current with a specific frequency in the circuit, reduce the AC components mixed in the DC voltage as much as possible, make the output waveform more stable, and achieve the purpose of reducing the ripple coefficient. The commonly used filtering method is to use devices with a specific impedance effect on AC signals, including capacitors and inductors. In this application, capacitor filtering is selected.

[0083] Based on the above selection of rectifier and filter circuits, the energy harvesting circuit in this application, the full-bridge rectifier-capacitor filter circuit, is designed, and its circuit connection method is as shown in the appendix Figure 3 as shown. The alternating current first passes through the full-wave bridge rectifier circuit and then is output to the load after capacitor filtering. Among them, C r is the filter capacitor, and R L is the analog load. When the input voltage reaches the sum of the voltage across the filter capacitor and the conduction voltages of diodes D2 and D3 (or D1 and D4) V D (i.e., |V in (t)| ≥ V L + 2V D ), the circuit can work normally. At this time, C r is charged and energy is supplied to R L . When the input voltage fails to reach the sum of the voltage across the filter capacitor and the conduction voltages of diodes D2 and D3 (or D1 and D4) (i.e., |V in (t)| ≤ V L + 2V D ), the circuit cannot conduct and work. At this time, the capacitor C r discharges and supplies energy to the load R L . The circuit waveform diagram is as shown in the appendix Figure 4 as shown.

[0084] Based on the above full-bridge rectifier-capacitor filter circuit, the LTC3588-1 chip is selected as the energy harvesting circuit. The LTC3588-1 chip is an energy management chip with ultra-low quiescent current, specifically designed for energy harvesting or low-current buck conversion. The LTC3588-1 integrates a low-loss full-wave bridge rectifier circuit and a high-efficiency buck converter inside, providing a complete energy harvesting management solution for high-output impedance energy sources such as piezoelectric conversion. This chip has an ultra-low quiescent current under-voltage lockout (UVLO) mode with a wide hysteresis window, which can store charge on the input capacitor and then effectively transfer part of the stored charge to the output through the buck converter. The LTC3588-1 can operate in the range of 2.7V to 20V, with an output current up to 100mA, and provides 4 output voltages: 1.8V, 2.5V, 3.3V, and 3.6V. The output voltage is selected by inputting high and low levels through two pins D0 and D1.

[0085] Table 1 LTC3588-1 Output Voltage Selection Table

[0086]

[0087] This power management chip can avoid higher output current bursts by adjusting the size of the output capacitor. It has a 20V input protection shunt that can provide greater energy storage for a certain number of input capacitors. A full-wave bridge rectifier is integrated inside the LTC3588-1, which can be directly accessed through the PZ1 and PZ2 differential inputs, and can directly rectify the AC input from piezoelectric and electromagnetic energy harvesting devices, and store the rectified output on the capacitor of the pin. This capacitor can also be used as an energy storage element for the buck converter. The internal structure block diagram of the chip is as shown in the appendix Figure 5 shown.

[0088] According to the data sheet and internal logic block diagram of the LTC3588-1 chip, its pin logic functions can be simply analyzed as shown in Table 2 below.

[0089] Table 2 LTC3588-1 Pin Function Table

[0090]

[0091] From the basic functions of the LTC3588-1, it can be seen that this chip is very suitable for use as the energy harvesting management of piezoelectric and low-power electromagnetic energy harvesting. C1 and C3 use supercapacitors, which can meet the rectification requirements while storing electrical energy, playing the role of capturing electrical energy. Supercapacitors have a longer lifespan than batteries, can be charged and discharged hundreds of thousands of times repeatedly, are easy to use, do not require a separate charge and discharge circuit, have low working requirements, and have high energy conversion efficiency, which is beneficial to the storage of micro electrical energy.

[0092] Connect the output terminals of the broadband energy harvesting device body to the and pins of the LTC3588-1 chip respectively. The energy harvesting circuit based on the LTC3588-1 chip is connected to the energy harvesting device as shown in the attached figure. Figure 6 as shown.

[0093] S3: Conduct piezoelectric experiment platform tests on the piezoelectric ceramic sheets used in the broadband energy harvesting device body in step S1;

[0094] To complete the piezoelectric energy harvesting experiment, an experimental platform needs to be built. The instruments and devices to be prepared are: a vibration test bench, piezoelectric materials, and corresponding support structures. In addition, the detection and observation instrument is an oscilloscope.

[0095] The vibration test bench uses an electromagnetic vibration test bench produced by Yibofan Environmental Equipment Company. This test bench can realize functions such as sine wave, frequency modulation, sweep frequency, multiple frequency, amplitude, and time control. It adopts a 7-inch touch screen, has strong anti-interference ability of the system, high control precision, convenient wiring, and strong expandability. It is suitable for low-frequency experiments in industries such as electronic devices and electrical instruments and meters, such as quality factor determination experiments, and evaluating the tolerance and reliability of structures.

[0096] In this application, the piezoelectric ceramic sheet 5 selects a piezoelectric ceramic sheet with a copper substrate covering PZT5 material. The copper substrate can ensure the toughness of the material and prevent the ceramic layer from being easily broken. Compared with other ceramics, PZT (lead zirconate titanate) ceramics are smaller in volume, higher in sensitivity, and higher in temperature tolerance. Its performance parameters are shown in Table 3 below.

[0097] Table 3 Performance Parameters of Piezoelectric Ceramic Sheets of PZT5 Material

[0098] Copper substrate thickness 0.25mm Substrate length 80mm Ceramic chip thickness 0.2mm Ceramic chip length 60mm Width 30mm Nominal frequency 28K Load impedance 100Ω Ceramic chip material PZT5 Equivalent capacitance 102nf Maximum output voltage 20V

[0099] When it undergoes deformation in the thickness direction, a direct piezoelectric effect will occur, and a pressure difference will be formed on both sides. The piezoelectric ceramic is attached tightly to the elastic thin sheet (the elastic thin sheet is 150 mm long, 30 mm wide, and 2 mm thick, and the piezoelectric ceramic substrate is 10 mm away from the fixed point of the support sheet). One end is fixedly connected to the vibration test bench to form the structure of a cantilever beam. A corresponding experimental support structure is designed as shown in the attached figure. Figure 7 as shown.

[0100] First, assemble the test bench completely, test the energy harvesting situation of the piezoelectric ceramic sheet. Adjust the vibration mode of the test bench to vertical, select a frequency of 20 Hz, and an intensity of 45%, and start the experiment. Obtain the direct output waveform of the piezoelectric ceramic sheet, which is displayed by the oscilloscope as shown in the attached figure. Figure 8 as shown.

[0101] From the attached figure Figure 8It can be seen that under this experimental environment, the output waveform of the piezoelectric ceramic sheet is similar to a sine wave, showing regular periodic changes. The peak-to-peak value reaches 6.40V, and the maximum value is 3.40V. To explore the influence of the vibration frequency on the piezoelectric energy harvesting efficiency, the vibration intensity was gradually increased from 5% to 40%. With the vibration frequency as the independent variable, the maximum values of the directly output waveform voltage were recorded as shown in Table 4 below.

[0102] Table 4 Piezoelectric power generation test data table

[0103]

[0104] To facilitate finding the pattern, a frequency-voltage graph was drawn based on the test data as shown in the appendix Figure 9 as shown. It can be seen from the appendix Figure 9 that under the same vibration intensity, there is a specific vibration frequency at which the output voltage reaches the maximum value, and this frequency is the resonance frequency; as the vibration intensity increases, the resonance frequency becomes higher, and the maximum output voltage also increases.

[0105] S4: Conduct on-vehicle piezoelectric tests on the piezoelectric ceramic sheets used in the broadband energy harvesting device body in step S1, and assemble weight pieces on the elastic thin sheet;

[0106] Specifically, fix the ceramic piezoelectric sheet 5 of the broadband energy harvesting device on the base, and then install it at the position of the vehicle wheel hub (due to the compact space at the vehicle wheel hub position, in order to ensure the movement space, an elastic thin sheet with a length of 110mm, a width of 30mm, and a thickness of 2mm is selected). Connect the ceramic piezoelectric sheet 5 to the oscilloscope using a conductive slip ring, supply power to the oscilloscope using an uninterruptible power supply (UPS), and observe the output effect of the piezoelectric device through the oscilloscope; drive at different vehicle speeds on different road surfaces and observe the waveforms of the oscilloscope.

[0107] When the vehicle speed is 20Km / h and driving straight on a flat cement road surface, the observed waveform is as shown in the appendix Figure 10 as shown.

[0108] It can be seen from the appendix Figure 10 that the maximum output voltage of the ceramic piezoelectric sheet 5 is 840mV, the minimum value is -880mV, and the peak-to-peak value is 1.72V.

[0109] The vehicle speed was changed for testing, and the results are shown in Table 5 below.

[0110] Table 5 Cement road test

[0111]

[0112] It can be seen from the test data that when the vehicle speed is 16Km / h, the peak-to-peak value of the output voltage reaches the maximum value, which is 2V. This indicates that at this vehicle speed, the elastic sheet vibration is at the resonance frequency, but the peak-to-peak value of 2V still cannot achieve the predetermined voltage stabilization effect.

[0113] Since bumpy road conditions can enhance the vibration of the vehicle, therefore, slate roads and masonry roads with relatively poor flatness are used for experimentation. As shown in the appendix Figure 11 described, in the appendix Figure 11 , (a) is a cement road, (b) is a slate road, and (c) is a masonry road. The test results are shown in Table 6 below,

[0114] Table 6 Tests on Slate Roads and Masonry Roads

[0115]

[0116] On the masonry road at a speed of 14 Km / h, the piezoelectric power generation effect is the best, and the peak-to-peak value can reach 6.25 V, which has exceeded the voltage stabilization threshold of the circuit. However, the speed range that can achieve the voltage stabilization effect is small. In order to increase the voltage stabilization speed range, it is necessary to further improve the piezoelectric power generation efficiency.

[0117] Furthermore, a counterweight is added to the end of the elastic thin sheet of the piezoelectric ceramic. Specifically, a counterweight screw is used, which can increase the deformation moment of the cantilever beam during vibration and increase the amount of deformation.

[0118] After adding the counterweight screw to the end of the elastic thin sheet, the road surface test is carried out again, and the results are shown in Table 7 below.

[0119] Table 7 Piezoelectric Tests with Counterweight Screws

[0120]

[0121] Adding the counterweight screw does improve the power generation effect of the piezoelectric ceramic sheet. The power generation effect is better than that without the counterweight under various road conditions, and the speed range reaching the voltage stabilization threshold is widened under the masonry road condition.

[0122] Under the masonry road condition, when the vehicle speed is 14 Km / h, the circuit output effect is verified by connecting the circuit. The results are shown in the appendix Figure 12 as shown.

[0123] S5: Conduct an electromagnetic power generation experiment on the coil and permanent magnet core used in the broadband energy harvesting device body in step S1, and install restraint springs at both ends of the permanent magnet core.

[0124] Specifically, according to the electromagnetic induction condition, coil 2 is wound into a cylindrical shape, and it is not difficult to see from the induced electromotive force expression that the more turns of the coil, the greater the induced electromotive force. Using enameled copper wire with good flexibility and low resistance as the raw material, it is tightly wound into a cylindrical shape on the support structure to study the electromagnetic power generation effect; when the vehicle speed is 10 Km / h, the electromagnetic power generation effect is tested on the cement road surface as shown in the appendix Figure 13 as shown. From the appendix Figure 13It can be seen that the peak-to-peak value shown on the oscilloscope is only 440 mV, and the waveform does not change periodically. Since the moving plane of the magnetic core is perpendicular to the rotating axis of the tire, the magnetic core will stay at one end of the coil due to centrifugal force when the tire rolls, forming a dead zone for the movement of the magnetic core.

[0125] According to the principle of the full-bridge rectifier-capacitor filter circuit, calculate the voltage output from the broadband energy harvesting device to both ends of the load; install constraint springs at both ends of the permanent magnetic core. The springs will give the magnetic core a balancing force, making the magnetic core always tend to stay in the middle position. Adjust the length and wire diameter of the constraint springs according to the voltage at both ends of the load.

[0126] The specific operation of calculating the voltage output from the broadband energy harvesting device to both ends of the load according to the principle of the full-bridge rectifier-capacitor filter circuit is as follows: Let the load voltage V L (that is, V DC ) remain constant. During the change period of the input voltage curve [t1, t3], due to the law of conservation of charge, the total amount of input charge is equal to the sum of the charge output to the load R L and the charge flowing through the capacitor C r . Since the load voltage V L is stable, so

[0127]

[0128] In the formula, R L is the equivalent load resistance; T is the modulation signal period; I is the circuit current;

[0129] Calculating the above formula gives

[0130]

[0131] In the formula, U M represents the amplitude of the vibration displacement; α represents the piezoelectric stress factor; C1 represents the equivalent capacitance of the piezoelectric sheet; ω is the vibration angular frequency;

[0132] Then the load voltage is expressed as

[0133]

[0134] From the above formula, the collection power of the circuit is

[0135]

[0136] Let:

[0137]

[0138] Then the optimal output load is

[0139]

[0140] The maximum output power is

[0141]

[0142] At this time, the voltage across the load is

[0143]

[0144] Select a piezoelectric spring with a wire diameter of 0.8 mm and a length of 50 mm. After installing the restraint spring, test the electromagnetic power generation effect again. The results are shown in Table 8 below.

[0145] Table 8 Electromagnetic Power Generation Test on Different Road Surfaces

[0146]

[0147] After installing the restraint spring, the characteristics of electromagnetic power generation and piezoelectric power generation are similar. The power generation effect is better under more bumpy and complex road conditions. However, in addition to the road conditions, the stiffness coefficient of the restraint spring will also affect the electromagnetic power generation efficiency. Test with restraint springs of different softness and hardness.

[0148] After the previous electromagnetic power generation experiment, it was found that the power generation efficiency is always the highest when the vehicle speed is 12 Km / h. Therefore, test directly at a speed of 12 Km / h on a brick road surface with different restraint springs.

[0149] Table 9 Electromagnetic Power Generation Test with Different Restraint Springs

[0150]

[0151] The experimental results show that the power generation effect is the best when using a restraint spring with a length of 50 mm and a wire diameter of 0.4 mm.

[0152] Example 3:

[0153] Example 3 conducts circuit verification on the energy harvesting circuit based on the LTC3588-1 chip in Example 2.

[0154] Use LTspice simulation software to conduct a simulation experiment. Use an AC current source (peak current is 1 mA, frequency is set to 20H z , and the waveform is a sine wave) in parallel with a capacitor (200 nF) to simulate the output of the energy harvesting device, and use a resistor (55 KΩ) to simulate the load. Design the circuit as shown in the appendix Figure 14 as shown.

[0155] Run the circuit and observe the waveform through the load as shown in the appendix Figure 15 as shown.

[0156] The simulation shows that this circuit can convert alternating current into direct current, and the output direct current voltage is stable at 3.6V. According to the previously designed circuit, the overall PCB circuit is designed using circuit simulation and PCB design software Altium Designer, as shown in the appendix Figure 16 as follows

[0157] Then select the components, list the BOM form, manufacture the PCB board, and perform component soldering processing on the printed circuit according to the schematic diagram

[0158] Table 3 PCB Circuit Component Information Table

[0159]

[0160] The physical PCB board processed is as shown in the appendix Figure 17 as follows

[0161] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents

Claims

1. Design method for a broadband energy harvesting device integrated with sensors inside automotive tires. The broadband energy harvesting device includes a broadband energy harvesting device body, and the broadband energy harvesting device body includes a first fixing bracket (1), a coil (2), and a permanent magnet core (3). An elastic thin sheet (4) is fixedly provided at the top of the first fixing bracket (1). One end of the elastic thin sheet (4) is fixedly connected to the first fixing bracket (1), the other end of the elastic thin sheet (4) is suspended, and a piezoelectric ceramic sheet (5) is provided on the elastic thin sheet (4). It is characterized in that, The design method includes the following steps S1: Design the structure of the broadband energy harvesting device body; S2: Design an energy harvesting circuit, select a chip, and connect it to the broadband energy harvesting device body to form a complete broadband energy harvesting device; S3: Conduct piezoelectric experiment platform tests on the piezoelectric ceramic sheet (5) used in the broadband energy harvesting device body in step S1; S4: Conduct in-vehicle piezoelectric tests on the piezoelectric ceramic sheet (5) used in the broadband energy harvesting device body in step S1, and install a weight (8) on the elastic thin sheet (4); S5: Conduct electromagnetic power generation experiments on the coil (2) and the permanent magnet core (3) used in the broadband energy harvesting device body in step S1, and install restraint springs (7) at both ends of the permanent magnet core (3); Among them, the specific operations of step S5 include the following steps S501: Conduct electromagnetic power generation experiments on the coil (2) and the permanent magnet core (3) used in the broadband energy harvesting device body; S502: Calculate the voltage output from the broadband energy harvesting device to both ends of the load according to the principle of a full-bridge rectification-capacitor filtering circuit; S503: Install restraint springs (7) at both ends of the permanent magnet core (3), and adjust the length and wire diameter of the restraint springs according to the voltage at both ends of the load in step S502.

2. The design method of the broadband energy harvesting device for an integrated sensor inside an automotive tire according to claim 1, characterized in that, The specific operations of step S4 include the following steps S401: Install the piezoelectric ceramic sheet (5) used in the broadband energy harvesting device body at the position of the vehicle wheel hub; S402: Connect the piezoelectric ceramic sheet (5) to an oscilloscope using a conductive slip ring; S403: Drive at different speeds on different road surfaces and observe the waveform of the oscilloscope.

3. The design method of the broadband energy harvesting device for the integrated sensor inside the automobile tire according to claim 1, characterized in that The specific operations of step S502 include the following steps Let the load voltage V L remain constant. During the change period of the input voltage curve [t1, t3], due to the law of conservation of charge, the total amount of input charge is equal to the sum of the charge output to the load and the charge flowing through the capacitor C r . Since the load voltage V L is stable and unchanged, so Wherein, R L is the equivalent load resistance; T is the modulation signal period; I is the circuit current; Calculating the above formula gives Wherein, U M represents the amplitude of the vibration displacement; a represents the piezoelectric stress factor; C1 represents the equivalent capacitance of the piezoelectric sheet; ω is the angular frequency of vibration; Then the load voltage is expressed as From the above formula, the collected power of the circuit is Let: Then the optimal output load is The maximum output power is At this time, the voltage at both ends of the load is 4. The design method of the broadband energy harvesting device for integrated sensors inside automotive tires according to claim 1, characterized in that: In the broadband energy harvesting device body, the coil (2) is cylindrical, the permanent magnet core (3) is cylindrical in structure, and the permanent magnet core (3) is located inside the coil (2). One end of the coil (2) is connected to the first fixing bracket (1), the other end of the coil (2) is connected to a second fixing bracket (6), and the first fixing bracket (1) and the second fixing bracket (6) are arranged in parallel; The broadband energy harvesting device body further includes a leveling component for adjusting the power generation effect of the device.

5. The design method of the broadband energy harvesting device for an integrated sensor inside an automotive tire according to claim 4, characterized in that: The leveling component includes restraint springs (7) fixedly provided at both ends of the permanent magnet core (3), and the ends of the two restraint springs (7) far from the permanent magnet core (3) are respectively connected to the corresponding first fixing bracket (1) or second fixing bracket (6).

6. The design method of the broadband energy harvesting device for the integrated sensor inside the automotive tire according to claim 5, characterized in that: The length of the constraint spring (7) is 50 mm, and the wire diameter is 0.4 mm.

7. The design method of the broadband energy harvesting device for the integrated sensor inside the automobile tire according to claim 6, characterized in that: The leveling assembly further includes a counterweight (8) detachably connected to the elastic sheet (4), and the counterweight (8) is located at one end of the elastic sheet (4) away from the first fixing bracket (1).

8. The design method of the broadband energy harvesting device for the integrated sensor inside the automotive tire according to claim 7, characterized in that: The wideband energy harvesting device further includes an LTC3588-1 chip, and the output end of the wideband energy harvesting device body is respectively connected to the PZ1 and PZ2 pins of the LTC3588-1 chip.

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