Flexible Internet of Things sensing aircraft node

Abstract

The invention relates to a flexible Internet of Things sensing aircraft node, which comprises a circuit board, and is characterized in that the circuit board is provided with a main control chip, an environment sensing sensor and a wireless transmission module; the main control chip is respectively connected with the environment sensor and the transmission module; the flying wing comprises a rectangular part and an isosceles trapezoid part, the longer bottom of the isosceles trapezoid part is connected with one long side of the rectangular part, and the shorter bottom of the isosceles trapezoid part is connected with the circuit board; the perpendicular bisector of the long bottom in the isosceles trapezoid part coincides with the perpendicular bisector of the long side in the rectangular part, and tearing lines are arranged along the perpendicular bisector of the long bottom in the isosceles trapezoid part and the perpendicular bisector of the long side in the rectangular part. The circuit board is an FPC (Flexible Printed Circuit); the flying wings are made of FPC flexible circuit boards. The device has the advantages of being simple in structure, small in size, easy to machine, low in cost, capable of achieving long-time floating without power and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of Internet of Things, and in particular to a flexible Internet of Things sensing aircraft node. Background Art

[0002] With the further development of large-scale Internet of Things (IoT) and wireless sensor technology, IoT sensing nodes have also shown great development potential and are widely used in smart cities, smart farms, smart safety monitoring, and smart fire protection. It has become an imperative task to deploy large-scale IoT nodes in emergency situations and remote areas to realize IoT data collection. In the research on large-scale rapid deployment, airdroppable IoT sensing nodes can effectively solve these problems. The integration of IoT nodes and various high-tech technologies has become a current development trend.

[0003] As drone delivery technology matures, if drones are used to perform large-scale airdrops of IoT nodes, the deployment cost of large-scale deployment of IoT nodes can be greatly reduced. Therefore, micro-aerial vehicles (MAV) technology can be used to carry IoT nodes, and drones can be used to airdrop micro-aerial vehicles.

[0004] Tsinghua University has worked with more than a dozen Chinese and foreign teams to develop the smallest man-made flying structure ever, which is even smaller than a pen refill and can spin and fall in the air like a seed. However, although a flying vehicle that is too small like a seed has a slow falling speed, it is difficult to design multifunctional complex circuits. It is difficult to integrate MCU with sensors and communication modules under the current printed circuit board and microelectronics technology. Therefore, designing a low-cost, unpowered micro-aircraft that can carry a large number of sensors and communication modules is an urgent problem to be solved in the emergency deployment of today's Internet of Things nodes. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a flexible Internet of Things sensing aircraft node, which has the advantages of simple structure, small size, easy processing, low cost, and the ability to float for a long time without power.

[0006] The technical solution adopted by the present invention to solve the technical problem is: to provide a flexible Internet of Things sensing aircraft node, including:

[0007] A circuit board, on which a main control chip, an environment perception sensor and a wireless transmission module are arranged; the main control chip is connected to the environment sensor and the transmission module respectively;

[0008] The flying wing comprises a rectangular part and an isosceles trapezoidal part, wherein the longer bottom of the isosceles trapezoidal part is connected to a long side of the rectangular part, and the shorter bottom of the isosceles trapezoidal part is connected to the circuit board; the perpendicular bisector of the longer bottom of the isosceles trapezoidal part coincides with the perpendicular bisector of the long side of the rectangular part, and a tear line is arranged along the perpendicular bisector of the longer bottom of the isosceles trapezoidal part and the perpendicular bisector of the long side of the rectangular part;

[0009] The circuit board is an FPC flexible circuit board; the flying wing is made of the FPC flexible circuit board.

[0010] The length of the longer base of the isosceles trapezoidal portion is equal to the length of one of the longer sides of the rectangular portion.

[0011] The included angle between the waist of the isosceles trapezoidal part and the short side of the rectangular part is 120° to 150°.

[0012] The environmental sensing sensor includes: a temperature and humidity sensor for detecting the temperature and humidity of the environment; an ambient light sensor for detecting the light intensity of the environment; and a chemical film sensor for detecting the chemical components to be tested in the environment.

[0013] The wireless transmission module is a LoRa module.

[0014] A printed antenna connected to the wireless transmission module is arranged on the FPC flexible circuit board; the printed antenna is a 1 / 4 wavelength monopole serpentine printed antenna.

[0015] The length of the 1 / 4 wavelength monopole serpentine printed antenna is: Among them, L εr is the length of the 1 / 4 wavelength monopole serpentine printed antenna, λ is the wavelength, ε eff is the effective dielectric constant of the FPC flexible circuit board, expressed as: ε r is the dielectric constant of the FPC flexible circuit board, h is the thickness of the FPC flexible circuit board, and w is the width of the 1 / 4 wavelength monopole serpentine printed antenna.

[0016] Beneficial Effects

[0017] Due to the adoption of the above-mentioned technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention adopts an FPC flexible circuit board to form a structure with the wing on top and the circuit board on the bottom. This structure can not only perfectly accommodate the main control chip, the wireless transmission module and various environmental perception sensors in the smallest size, but also when the wingspan of the wing is 8 cm and the angle between the wing and the circuit board is 135°, the upper and lower pressure difference at the terminal speed can be maximized. At this time, it can provide lift to the aircraft to the greatest extent to slow down the falling speed, and it has a very stable falling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a flexible Internet of Things sensing aircraft node according to an embodiment of the present invention;

[0019] Figure 2 It is a schematic diagram of the structure of the flexible Internet of Things sensing aircraft node after the wings are unfolded according to an embodiment of the present invention;

[0020] Figure 3 It is a flow trace diagram obtained after simulating the flexible Internet of Things sensing aircraft node in the implementation mode of the present invention;

[0021] Figure 4 It is a schematic diagram of the eddy current generated after simulating the flexible Internet of Things sensing aircraft node in the implementation mode of the present invention;

[0022] Figure 5 is a hardware system block diagram of the circuit board part in an embodiment of the present invention;

[0023] Figure 6 It is a reset circuit diagram of a microcontroller of a main control chip in an embodiment of the present invention;

[0024] Figure 7 is a circuit diagram of a temperature and humidity sensor in an embodiment of the present invention;

[0025] Figure 8 is a collection circuit diagram of an ambient light sensor in an embodiment of the present invention;

[0026] Fig. 9 is a circuit diagram of a chemical film sensor according to an embodiment of the present invention;

[0027] Fig.10 is a schematic diagram of a model of a printed antenna in an embodiment of the present invention;

[0028] Fig.11 is a simulation diagram of the S11 parameters of the printed antenna in an embodiment of the present invention;

[0029] Fig.12 is a 2D directional pattern of a printed antenna in an embodiment of the present invention;

[0030] Fig.13 : is an application circuit diagram of the voltage stabilizing chip TPS61040 in an embodiment of the present invention;

[0031] Fig.14 It is a simulation schematic diagram of a flexible Internet of Things sensing aircraft node according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0033] The embodiments of the present invention relate to a flexible IoT sensing aircraft node, such as Figure 1 As shown, it includes: a circuit board 1, on which a main control chip, an environment perception sensor and a wireless transmission module are arranged; the main control chip is connected to the environment sensor and the transmission module respectively; a flying wing 2, including a rectangular part 21 and an isosceles trapezoidal part 22, the longer bottom of the isosceles trapezoidal part 22 is connected to a long side of the rectangular part 21, and the shorter bottom of the isosceles trapezoidal part 22 is connected to the circuit board 1; the perpendicular midline of the longer bottom of the isosceles trapezoidal part 22 coincides with the perpendicular midline of the long side of the rectangular part 21, and a tear line 3 is arranged along the perpendicular midline of the longer bottom of the isosceles trapezoidal part 22 and the perpendicular midline of the long side of the rectangular part 21. Wherein, the circuit board 1 is an FPC flexible circuit board; the flying wing 2 is made of an FPC flexible circuit board.

[0034] The flexible IoT sensing aircraft node of this embodiment abandons the traditional FR4 material hard circuit board and uses FPC flexible circuit board for design, miniaturizing and integrating the circuit board part, and controlling the size of the circuit board part within 3cm×5cm. The selection of components also implements miniaturization and lightweight selection, which not only effectively reduces the weight of the circuit board, but also leaves a large area of ​​the FPC flexible circuit board as the dual-rotor flight structure of the IoT sensing node. When using this embodiment, you only need to divide the flying wing into two halves along the tear line, and bend one half to the front of the circuit board part, and the other half to the back of the circuit board part, so as to form a Figure 2 The shape shown. The flexible IoT sensing aircraft node of this shape has two rotors that are bent outwards and in opposite directions. When it falls, the rotors will provide it with upward lift.

[0035] The overall size of the flexible IoT sensing aircraft node of this embodiment is 10cm×8cm, and the thickness is only 0.11mm, which is as thin as an ordinary A4 paper. After many falling experiments, it is determined that the falling effect is best when the long side of the rectangular part 21 in the flying wing and the longer base of the isosceles trapezoidal part 22 are both 8cm and the angle between the waist of the isosceles trapezoidal part 22 and the short side of the rectangular part 21 is 135°, so that the rotor of the flexible IoT sensing aircraft node has a large enough frontal area, and it will land at a relatively slow speed when falling.

[0036] The circuit board part in this embodiment will be equipped with a main control chip, a variety of environmental perception sensors, wireless transmission modules and other devices, which greatly increases the use value of the flexible Internet of Things perception aircraft node. And because the circuit board part is mainly concentrated at the bottom of the flexible Internet of Things perception aircraft node, the center of gravity of the flexible Internet of Things perception aircraft node is low, so that the flexible Internet of Things perception aircraft node has sufficient stability during the rotation and falling process.

[0037] In order to further analyze the aerodynamic characteristics of the flexible IoT sensing aircraft node when it falls and verify the feasibility of the flight structure, the fluid simulation plug-in Flow Simulation in Solidworks will be used to simulate the air fluid of the flexible IoT sensing aircraft node when it falls. In order to increase the accuracy of computational fluid dynamics and simplify the establishment of the model, the components of the flexible IoT sensing aircraft node are partially thickened for equivalent, which is more conducive to the analysis and observation of the fluid model.

[0038] This simulation uses a cubic computational domain to wrap the flexible IoT sensing aircraft node located in a unidirectional flow wind field, and establishes a rotation area for it to simulate the rotation fall. The boundary condition parameter values ​​set in computational fluid dynamics are shown in Table 1:

[0039] Table 1. Table of parameter values ​​for setting simulation boundary conditions

[0040]

[0041] The ability to stay in the air during the descent of the flexible IoT sensing aircraft node is a key factor in the long-term free flight of a micro-aircraft in the air, and the terminal velocity (the final velocity reached in a uniform descent state) is an important indicator to measure its ability to stay in the air. Figure 3This is the flow trajectory diagram of static pressure obtained after the simulation calculation is completed. This simulation simulates the changes in surrounding pressure and air velocity when the flexible IoT sensing aircraft node rotates and falls. The fluid flowing through the flexible IoT sensing aircraft node produces a significant pressure difference between the upper and lower parts of the model, which provides lift for the flexible IoT sensing aircraft node when it falls. Therefore, it can fall with the wind at a slow terminal speed when it falls, which provides a guarantee for the safe landing of the IoT sensing node. Figure 4 As shown, the flexible IoT sensing aircraft node obtains high lift by generating a stable leading-edge vortex (LEV) during the falling process. The flexible IoT sensing aircraft node is a passive autorotating aircraft, which falls slower than a non-autorotating aircraft and has higher falling stability. In addition, the flexible IoT sensing aircraft node adopts a dual-rotor structure. Compared with some single-rotor wind-transmitted seeds, the center of the dual-rotor structure is centered, which can stabilize the rotation angle during the falling process. Therefore, the stability of the flexible IoT sensing aircraft node of this embodiment will be further improved.

[0042] like Figure 5 As shown, this embodiment uses PIC18 as the main control chip and the LoRa module as the wireless transmission module. The flexible IoT sensing aircraft node of this embodiment is powered by a DC-DC power supply, and the operating voltage is set to 3.3V. The main control chip interacts with the LoRa module through USART, and can perform initialization settings of the LoRa module, read and write data, and send and receive instructions.

[0043] The main control chip of the flexible Internet of Things sensing aircraft node of this embodiment can use the PIC18F26K80 of the PIC18 series. The microcontroller adopts a 28-pin QFN (Quad Flat No-lead Package) package, and the chip size is only 6mm×6mm×0.9mm. Figure 6 The microcontroller reset circuit diagram is given, which adds an additional resistor between the MCLR pin and the power supply terminal VDD. This resistor can help stabilize the voltage of the MCLR pin and prevent accidental reset due to power supply fluctuations.

[0044] The environment perception sensor of the flexible Internet of Things perception aircraft node of this embodiment includes a temperature and humidity sensor for detecting the temperature and humidity of the environment; an ambient light sensor for detecting the light intensity of the environment; and a chemical film sensor for detecting the chemical components to be tested in the environment.

[0045] Among them, the temperature and humidity sensor can use Sensirion's SHT3x-ARP chip, which can provide more accurate and stable temperature and humidity measurements through enhanced signal processing functions. The SHT3x-ARP chip uses a DFN package with a size of 2.5×2.5mm and a height of 0.9mm, which is conducive to the miniaturization and lightweight design of flexible IoT sensing aircraft nodes. Figure 7 This is a typical application circuit diagram of the SHT3x-ARP chip. The sensor supports 2.4V-5.5V power supply. Therefore, this implementation selects 3.3V of the power supply terminal VDD to power the temperature and humidity sensor, where T is the temperature analog voltage output and RH is the humidity analog voltage output. The output range is 10% to 90% proportional analog voltage output, with a typical accuracy of 2% RH and 0.3°C. The PIC18 microcontroller will use the 12-bit analog input pin to collect data from the temperature and humidity sensor.

[0046] The ambient light sensor can use ALS-PT19-315C / L177 / TR8, which is packaged in the form of a patch, has a small size, and can collect sensor signals through a simple voltage conversion circuit. Figure 8 The circuit form converts the photocurrent and output voltage into a voltage form that can be smoothly collected by the microcontroller. The PIC18 microcontroller will use the 12-bit analog input pin to collect the data of the ambient light sensor.

[0047] The FPC flexible circuit board used in the flexible IoT sensing aircraft node of this embodiment is mainly made of polyimide, and the physical properties of polyimide provide favorable conditions for the coating of chemical thin film sensors. In this embodiment, the flexible IoT sensing aircraft node reserves an interface for the chemical thin film sensor, and the required chemical thin film sensor can be mounted on the IoT sensing node through chemical coating technology to realize the detection of special substances in specific occasions. Fig. 9 U6 in the figure is a chemical film sensor. By connecting the chemical film sensor in series with a resistor, the chemical reaction of the chemical film sensor can be reflected in the form of voltage change. The 12-bit analog input of the PIC18 microcontroller is used to collect the voltage signal to determine the degree of chemical reaction of the chemical film sensor. In this embodiment, the size of the central coating area of ​​the package corresponding to the chemical film sensor is 5mm×5mm.

[0048] In this implementation, the PIC18 microcontroller uses high-precision analog pins to collect and determine the light intensity, ambient temperature and humidity of the IoT sensing node, and then uses the voltage signal of the chemical film sensor to analyze the overall environmental information. The IoT sensing node equipped with a variety of environmental sensing sensors will play a huge application value in industrial environmental monitoring, disaster sites, and polluted areas.

[0049] The LoRa module in this embodiment can adopt the ATK-LoRa-02_V1.5 launched by ALIENTEK, which is a high-performance LoRa wireless serial port module. It relies on advanced SMD packaging technology to achieve a perfect combination of low power consumption, compact design and remote communication. Based on the ISM band RF SX1278 chip, the module provides up to 32 channel options in the range of 410Mhz to 441Mhz. The receiving sensitivity of the ATK-LoRa-02_V1.5 module can reach -136dBm, so it has a reliable and stable communication distance. At the same time, its low-power design and air wake-up function enable the module to keep monitoring the signal even in standby mode, thereby achieving a more energy-saving communication method. In addition, the module also has a dual 512 ring FIFO buffer, which can effectively ensure the continuity and stability of data transmission.

[0050] In order to meet the miniaturization and lightweight design of the flexible IoT sensing aircraft node of this embodiment, this embodiment adopts onboard antenna technology, that is, a printed antenna connected to the LoRa module is set on the FPC flexible circuit board. When designing a printed antenna, the dielectric constant of the dielectric board and the partial influence of the surrounding air are crucial considerations. Through in-depth research on the characteristic impedance of the microstrip transmission line, it is found that the effective dielectric constant of the dielectric substrate of the printed antenna is closely related to the equivalent dielectric constant of the microstrip line. In order to ensure that the printed antenna has the required gain performance, it is usually required that the ratio of the width w of the antenna to the thickness h of the dielectric substrate exceeds 1 (ie w / h>1). Based on this design criterion, this embodiment uses the following mathematical expression to estimate the effective dielectric constant of the printed antenna dielectric substrate:

[0051]

[0052] Among them, ε eff is the effective dielectric constant of the FPC flexible circuit board, ε r is the dielectric constant of the FPC flexible circuit board, h is the thickness of the FPC flexible circuit board, and w is the width of the printed antenna. It can be concluded that the length of the monopole printed antenna is:

[0053]

[0054] Among them, L εr is the length of the printed antenna and λ is the wavelength.

[0055] According to the above formula, combined with the thickness and dielectric constant of the FPC flexible circuit board, the length of the 433MHz monopole antenna is calculated to be between 86.5 and 173mm. Fig.10As shown, this embodiment adopts a modified form of the inverted F antenna for antenna design. The antenna occupies an area of ​​20×40mm. The antenna is a 1 / 4 wavelength monopole serpentine printed antenna. After simulation analysis, the S11 parameters of the printed antenna are as follows Fig.11 As shown, its S11 parameter at 433MHz can reach below -14dB. Fig.12 is a 2D directional map.

[0056] As a low-cost, disposable, and large-scale airdrop IoT node, IoT batteries have become the first choice for the flexible IoT sensing aircraft node of this embodiment. In view of the unique battery requirements of IoT scenarios, the sensor battery has three major characteristics: large capacity, resistance to attenuation, and strong response, which can achieve instantaneous explosive power and long-term endurance at the same time. The sensor battery (CR1220) has a diameter of 1.2cm, a thickness of 0.2cm, and a battery capacity of 40mAh. Its tiny size and extremely light weight are very suitable for use in airdrop IoT nodes. The average operating current of the flexible IoT sensing aircraft node of this embodiment is 8mA, so a CR1220 sensor battery can work continuously for 5 hours.

[0057] However, the output voltage of the sensor battery is 3V. According to the hardware design and low power consumption requirements of the flexible IoT sensing aircraft node of this embodiment, the module needs to work at a voltage of 3.3V. Therefore, this embodiment also uses a DC-DC converter built with a voltage regulator chip TPS61040 to convert direct current from one voltage to another. Fig.13 As shown, when the input is 3V, the design according to the device size in the figure will output a 5V voltage. However, the flexible Internet of Things sensing aircraft node in this embodiment requires a 3.3V power supply, so only the resistance value of resistor R1 needs to be adjusted to 340kΩ to obtain a 3.3V voltage output.

[0058] Fig.14 What is shown is a simulation schematic diagram of the flexible Internet of Things sensing aircraft node of this embodiment, which is equipped with a PIC18 single-chip microcomputer, a single-chip microcomputer peripheral circuit, a DC-DC voltage regulator module, a temperature and humidity sensor, an ambient light sensor, a chemical film sensor, a button battery and a debugging interface on the front of the bottom of the flexible Internet of Things sensing aircraft node, and a LoRa communication module and another chemical film sensor on the back. Among them, the packaging of the capacitor and the resistor are both 0402, which provides favorable conditions for the miniaturization of the flexible Internet of Things sensing aircraft node. At this time, it is only necessary to divide the flying wing into two parts along the tear line to form two wings, bend one wing toward the front of the circuit board part, and bend the other wing toward the reverse side of the circuit board part. The shape formed at this time has the characteristics of falling rotation.

[0059] It is not difficult to find that the present invention adopts FPC flexible circuit board to form a structure with the wing on top and the circuit board on the bottom. This structure can not only perfectly accommodate the main control chip, wireless transmission module and various environmental perception sensors in the smallest size, but also when the wingspan of the wing is 8cm and the angle between the wing and the circuit board is 135°, the upper and lower pressure difference of the terminal speed can be maximized. At this time, it can provide lift to the aircraft to the greatest extent to slow down the falling speed, and it has a very stable falling performance.

Claims

1. A flexible Internet of Things sensing aircraft node, characterized in that: include: A circuit board, on which a main control chip, an environment perception sensor and a wireless transmission module are arranged; the main control chip is connected to the environment sensor and the transmission module respectively; The flying wing comprises a rectangular part and an isosceles trapezoidal part, wherein the longer bottom of the isosceles trapezoidal part is connected to a long side of the rectangular part, and the shorter bottom of the isosceles trapezoidal part is connected to the circuit board; the perpendicular bisector of the longer bottom of the isosceles trapezoidal part coincides with the perpendicular bisector of the long side of the rectangular part, and a tear line is arranged along the perpendicular bisector of the longer bottom of the isosceles trapezoidal part and the perpendicular bisector of the long side of the rectangular part; The circuit board is an FPC flexible circuit board; the flying wing is made of the FPC flexible circuit board.

2. The flexible Internet of Things sensing aircraft node according to claim 1 is characterized in that: The length of the longer base of the isosceles trapezoidal portion is equal to the length of one of the longer sides of the rectangular portion.

3. The flexible Internet of Things sensing aircraft node according to claim 1, characterized in that: The included angle between the waist of the isosceles trapezoidal part and the short side of the rectangular part is 120° to 150°.

4. The flexible Internet of Things sensing aircraft node according to claim 1, characterized in that: The environmental sensing sensor includes: a temperature and humidity sensor for detecting the temperature and humidity of the environment; an ambient light sensor for detecting the light intensity of the environment; and a chemical film sensor for detecting the chemical components to be tested in the environment.

5. The flexible Internet of Things sensing aircraft node according to claim 1, characterized in that: The wireless transmission module is a LoRa module.

6. The flexible Internet of Things sensing aircraft node according to claim 1, characterized in that: A printed antenna connected to the wireless transmission module is arranged on the FPC flexible circuit board; the printed antenna is a 1 / 4 wavelength monopole serpentine printed antenna.

7. The flexible Internet of Things sensing aircraft node according to claim 6, characterized in that: The length of the 1 / 4 wavelength monopole serpentine printed antenna is: Among them, L εr is the length of the 1 / 4 wavelength monopole serpentine printed antenna, λ is the wavelength, ε eff is the effective dielectric constant of the FPC flexible circuit board, expressed as: ε r is the dielectric constant of the FPC flexible circuit board, h is the thickness of the FPC flexible circuit board, and w is the width of the 1 / 4 wavelength monopole serpentine printed antenna.

Images