A flexible Internet of Things sensing aircraft node

Abstract

The present invention relates to a flexible Internet of Things sensing aircraft node, comprising: a circuit board, on which is disposed a main control chip, an environmental sensing sensor, and a wireless transmission module; the main control chip being connected to the environmental sensing sensor and the transmission module, respectively; a flying wing comprising a rectangular portion and an isosceles trapezoidal portion, wherein the longer base of the isosceles trapezoidal portion is connected to a long side of the rectangular portion, and the shorter base of the isosceles trapezoidal portion is connected to the circuit board; the perpendicular bisector of the longer base of the isosceles trapezoidal portion coincides with the perpendicular bisector of the longer side of the rectangular portion, and tear lines are provided along the perpendicular bisector of the longer base of the isosceles trapezoidal portion and the perpendicular bisector of the longer side of the rectangular portion; the circuit board is an FPC flexible circuit board; and the flying wing is manufactured using the FPC flexible circuit board. The present invention has the advantages of simple structure, small size, ease of processing, low cost, and the ability to achieve long-term levitation without the need for power.

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 technologies, IoT sensing nodes have shown tremendous potential for development, with widespread applications in smart cities, smart farms, smart safety monitoring, and smart fire protection. Deploying large-scale IoT nodes in emergency situations and remote areas to collect IoT data has become imperative. In research on large-scale, rapid deployment, airdroppable IoT sensing nodes can effectively address these challenges. The integration of IoT nodes with various high-tech technologies has become a current development trend.

[0003] As drone delivery technology matures, if drones are used to carry out 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, in collaboration with over a dozen Chinese and international teams, has developed the smallest man-made flying structure ever created. This structure, even smaller than a pencil refill, can spin and fall through the air like a seed. However, despite its slow descent speed, such a tiny flying vehicle is difficult to design with complex, multifunctional circuitry. Furthermore, integrating the MCU with sensors and communication modules is difficult with current printed circuit board and microelectronics processes. Therefore, designing a low-cost, unpowered micro-flyer capable of carrying a large number of sensors and communication modules is a pressing challenge for the emergency deployment of IoT 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 provided; the main control chip is connected to the environment perception sensor and the transmission module respectively;

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

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

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

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

[0012] The environmental perception 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 provided 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, and 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 solution, 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, 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 very stable falling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This 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 This 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 This is a flow trajectory diagram obtained after simulating a flexible Internet of Things sensing aircraft node in an embodiment of the present invention;

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

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

[0023] Figure 6 1 is a microcontroller reset circuit diagram of the 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] Figure 9 is a circuit diagram of a chemical film sensor according to an embodiment of the present invention;

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

[0028] Figure 11 1 is a simulation diagram of the S11 parameters of the printed antenna in an embodiment of the present invention;

[0029] Figure 12 is the 2D radiation pattern of the printed antenna in an embodiment of the present invention;

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

[0031] Figure 14 This 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] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, 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 equally within the scope limited by the appended claims of the application.

[0033] The embodiment of the present invention relates to a flexible Internet of Things sensing aircraft node, such as Figure 1 As shown, it comprises: a circuit board 1, on which is mounted a main control chip, an environmental perception sensor, and a wireless transmission module; the main control chip is connected to the environmental perception sensor and the transmission module, respectively; a flying wing 2, comprising a rectangular portion 21 and an isosceles trapezoidal portion 22, wherein the longer base of the isosceles trapezoidal portion 22 is connected to a long side of the rectangular portion 21, and the shorter base of the isosceles trapezoidal portion 22 is connected to the circuit board 1; the perpendicular midline of the longer base of the isosceles trapezoidal portion 22 coincides with the perpendicular midline of the longer side of the rectangular portion 21, and a tear line 3 is provided along the perpendicular midline of the longer base of the isosceles trapezoidal portion 22 and the perpendicular midline of the longer side of the rectangular portion 21. The circuit board 1 is a flexible printed circuit board (FPC); and the flying wing 2 is made of the same.

[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 the selection of miniaturization and lightweight. This 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, it is only necessary to split 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, thereby forming a Figure 2 The flexible IoT sensing aircraft node has two outward-bent rotors that move in opposite directions. When it falls, the rotors provide it with upward lift.

[0035] The flexible IoT sensing aircraft node in this embodiment has an overall size of 10cm x 8cm and a thickness of only 0.11mm, about the same thickness as a sheet of A4 paper. After multiple drop tests, it was determined that optimal drop performance was achieved when the long side of the rectangular portion 21 and the longer base of the isosceles trapezoidal portion 22 were both 8cm, and the angle between the waist of the isosceles trapezoidal portion 22 and the short side of the rectangular portion 21 was 135°. This ensured that the rotor of the flexible IoT sensing aircraft node had a sufficiently large frontal area, resulting in a relatively slow landing.

[0036] The circuit board part in this embodiment will be equipped with a main control chip, multiple 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 lower, so that the flexible Internet of Things perception aircraft node has sufficient stability during the rotation and falling process.

[0037] To further analyze the aerodynamic characteristics of the flexible IoT sensing aircraft node during its descent and verify the feasibility of the flight structure, the SolidWorks fluid simulation plug-in, Flow Simulation, was used to simulate the air flow during the descent of the flexible IoT sensing aircraft node. To increase computational fluid dynamics accuracy and simplify model creation, the components of the flexible IoT sensing aircraft node were thickened to create an equivalent structure, further facilitating analysis and observation of the fluid model.

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

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

[0040]

[0041] The ability to stay in the air during the descent of flexible IoT sensing aircraft nodes is a key factor in the long-term free flight of micro-aircraft in the air, and the terminal velocity (the final velocity reached in the 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. The 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 creates a significant pressure difference between the upper and lower parts of the model, which provides lift for the flexible IoT sensing aircraft node as it falls. Therefore, it can fall with the wind at a slow terminal speed, which ensures the safe landing of the IoT sensing node. Figure 4 As shown, the flexible IoT sensing aircraft node generates high lift by generating a stable leading-edge vortex (LEV) during descent. This flexible IoT sensing aircraft node is a passive autorotating aircraft, which descends more slowly and offers greater descent stability than non-autorotating aircraft. Furthermore, the flexible IoT sensing aircraft node utilizes a dual-rotor structure. Compared to some single-rotor wind-borne seeds, the dual-rotor structure has a centrally located center, which stabilizes the rotation angle during descent. Therefore, the stability of the flexible IoT sensing aircraft node in this embodiment is further enhanced.

[0042] like Figure 5 As shown, this embodiment uses a PIC18 as the main control chip and a LoRa module as the wireless transmission module. The flexible IoT sensing aircraft node in this embodiment is powered by a DC-DC power supply with an operating voltage set to 3.3V. The main control chip exchanges data with the LoRa module via a USART interface, enabling initialization of the LoRa module, data reading and writing, and the sending and receiving of commands.

[0043] The main control chip of the flexible Internet of Things sensing aircraft node in 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 environmental perception sensors of the flexible Internet of Things perception aircraft node in this embodiment include 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] The temperature and humidity sensor can use Sensirion's SHT3x-ARP chip, which, through enhanced signal processing capabilities, provides more accurate and stable temperature and humidity measurements. The SHT3x-ARP chip uses a DFN package with dimensions of 2.5 × 2.5 mm and a height of 0.9 mm, facilitating 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 embodiment selects the 3.3V power supply terminal VDD to power the temperature and humidity sensor. 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 pins 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 and has a small size. The sensor signal can be collected through a simple voltage conversion circuit. Figure 8 The circuit converts the photocurrent and output voltage into a voltage form that can be smoothly collected by the microcontroller. The PIC18 microcontroller uses the 12-bit analog input pin to collect the data of the ambient light sensor.

[0047] The flexible printed circuit board (FPC) used in the flexible IoT sensing aircraft node of this embodiment is primarily made of polyimide. 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 has a reserved interface for the chemical thin-film sensor. Through chemical coating technology, the required chemical thin-film sensor can be mounted on the IoT sensing node, enabling detection of specific substances in specific situations. Figure 9 U6 in the figure is a chemical film sensor. By connecting the chemical film sensor in series with a resistor, chemical reactions in the chemical film sensor are reflected in the form of voltage changes. The PIC18 microcontroller's 12-bit analog input is used to acquire the voltage signal, thereby determining the extent of the chemical film sensor's reaction. In this embodiment, the central coating area of ​​the chemical film sensor package is 5mm x 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. IoT sensing nodes equipped with multiple environmental sensing sensors will have great application value in industrial environment monitoring, disaster sites, and polluted areas.

[0049] The LoRa module in this embodiment can use the ATK-LoRa-02_V1.5 launched by ALIENTEK. This is a high-performance LoRa wireless serial port module. Leveraging advanced SMD packaging technology, it achieves the perfect combination of low power consumption, compact design, and long-distance communication. Based on the ISM band RF SX1278 chip, the module offers up to 32 channel options within the 410MHz to 441MHz range. The ATK-LoRa-02_V1.5 module boasts a receiving sensitivity of -136dBm, ensuring a reliable and stable communication distance. Furthermore, its low-power design and over-the-air wake-up function enable the module to maintain signal monitoring even in standby mode, achieving a more energy-efficient communication method. Furthermore, the module features dual 512-bit circular FIFO buffers, effectively ensuring the continuity and stability of data transmission.

[0050] In order to meet the miniaturization and lightweight design of the flexible Internet of Things sensing aircraft node of this embodiment, this embodiment adopts on-board 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 plate 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 antenna width w to the dielectric substrate thickness h exceeds 1 (that is, 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. From this, the length of the monopole printed antenna can be obtained as:

[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 roughly between 86.5 and 173mm. Figure 10As shown, this embodiment adopts a modified form of inverted F antenna for antenna design. The antenna occupies an area of ​​20×40mm. This antenna is a 1 / 4 wavelength monopole serpentine printed antenna. After simulation analysis, the S11 parameters of this printed antenna are as follows Figure 11 As shown, its S11 parameter at 433MHz can reach below -14dB. Figure 12 is a 2D directional pattern.

[0056] As a low-cost, disposable, and large-scale airdroppable IoT node, IoT batteries are the preferred choice for the flexible IoT sensing aircraft node in this embodiment. Addressing the unique battery requirements of IoT scenarios, the Transformer battery offers three key characteristics: high capacity, low degradation resistance, and strong responsiveness, enabling both instantaneous burst power and long-term endurance. The Transformer battery (CR1220) has a diameter of 1.2cm, a thickness of 0.2cm, and a capacity of 40mAh. Its small size and extremely light weight make it ideal for use in airdroppable IoT nodes. With an average operating current of 8mA for the flexible IoT sensing aircraft node in this embodiment, a single CR1220 Transformer battery can provide five hours of continuous operation.

[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 in this embodiment, the module needs to operate 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. Figure 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 it is only necessary to adjust the resistance value of resistor R1 to 340kΩ to obtain a 3.3V voltage output.

[0058] Figure 14 The figure shows a simulation diagram of a flexible IoT sensing aircraft node according to this embodiment. The front of the node is equipped with a PIC18 microcontroller, microcontroller peripheral circuits, 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. The back of the node is equipped with a LoRa communication module and another chemical film sensor. The capacitors and resistors are both packaged in 0402, which facilitates the miniaturization of the node. At this point, the wing is simply split into two parts along the tear line to form two wings. One wing is bent toward the front of the circuit board portion, and the other wing is bent toward the back of the circuit board portion. The resulting shape has the characteristics of falling and rotating.

[0059] It is not difficult to find that the present invention uses 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, 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 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 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 provided; the main control chip is connected to the environment perception sensor and the transmission module respectively; The wing comprises a rectangular portion and an isosceles trapezoidal portion, wherein the longer base of the isosceles trapezoidal portion is connected to one of the long sides of the rectangular portion, and the shorter base of the isosceles trapezoidal portion is connected to the circuit board; the perpendicular bisector of the longer base of the isosceles trapezoidal portion coincides with the perpendicular bisector of the longer side of the rectangular portion, and a tear line is provided along the perpendicular bisector of the longer base of the isosceles trapezoidal portion and the perpendicular bisector of the longer side of the rectangular portion; the length of the longer base of the isosceles trapezoidal portion is equal to the length of one of the long sides of the rectangular portion, and the angle between the waist of the isosceles trapezoidal portion and the shorter side of the rectangular portion is 120° to 150°; The circuit board is an FPC flexible circuit board; the flying wing is made of an FPC flexible circuit board.

2. The flexible Internet of Things sensing aircraft node according to claim 1, characterized in that: The environmental perception 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.

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

4. 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 provided on the FPC flexible circuit board; the printed antenna is a 1 / 4 wavelength monopole serpentine printed antenna.

5. The flexible Internet of Things sensing aircraft node according to claim 4, 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, and 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.

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