A downhole equipment communication system and method based on visible light

Abstract

The present invention relates to the field of communication technology, and discloses a downhole equipment communication system and method based on visible light, as well as downhole equipment and a control method thereof. The system comprises: a control end for generating a control signal, a transmitting end for transmitting an optical signal into an air channel, and a receiving end for receiving the optical signal and restoring it into a control signal; the control end is connected to the transmitting end for transmitting the control signal; the transmitting end comprises a light source whose luminous characteristics conform to the characteristics of a Lambertian point light source, and a multi-stage voltage amplification control module for controlling the flashing of the light source according to the control signal; the receiving end comprises a photodiode for converting the captured optical signal into an electrical signal, a transimpedance amplification module for amplifying the converted signal, and a signal processing module for restoring the control signal. The present invention can achieve reliable data transmission while providing uniform illumination, improve communication rate and anti-interference capability, and ensure adaptability and stability in harsh environments.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a downhole equipment communication system and method based on visible light, and downhole equipment and a control method thereof. Background Art

[0002] With the continued advancement of industrialization, my country's demand for mineral resources continues to increase. This enormous market demand places higher demands on the mining industry. The 14th Five-Year Plan for a Modern Energy System points out that the transformation of energy production and consumption patterns toward green and low-carbon development is the primary direction of future development. It vigorously promotes the construction of green and digital mines, and prioritizes safe and efficient mine production as a key development area. Mine communications, as a crucial foundation for the digital development of the mining industry, will be a key area in the future of intelligent mine production.

[0003] As mine production becomes increasingly intelligent, ensuring the stability and efficiency of communication systems throughout the production process is a critical and pressing issue. Due to the harsh underground environment, specialized production methods, and complex production processes, the stability, reliability, and safety of communication systems face significant challenges. Currently, widely used underground radio frequency communication systems (RFCs) face challenges in the harsh underground environment of high dust and humidity. These systems are affected by dust particles and water molecules in the air, causing signal attenuation and multipath interference, resulting in high bit error rates and poor signal quality. Furthermore, electromagnetic effects introduced during communication pose a significant threat to mine safety. Other RF communication systems, such as leaky RF communication systems, rely directly on cables for data transmission. These systems transmit and receive information via specialized cables, making their reliability dependent on leaky cables. These cables are sensitive to the external storage environment, and the harsh environment accelerates cable aging and wear, leading to increased signal loss and reduced quality. Furthermore, the numerous underground devices connected to the cables generate a significant amount of interference during operation, which can easily lead to unstable transmission. Summary of the Invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention introduces visible light communication technology into mine communications. Visible light communication transmits data through optical signals. This process is not affected by electromagnetic interference generated by motors, cables and other equipment in the mine environment, and no electromagnetic radiation is generated during the communication process, thereby ensuring the stability and security of the communication process; the communication system is combined with the existing lighting system to reduce the probability of independent equipment failure and improve the overall reliability of the system.

[0005] The present invention discloses a downhole equipment communication system based on visible light, comprising: a control end for generating a control signal, a transmitting end for transmitting the optical signal into an air channel, and a receiving end for receiving the optical signal and restoring it into a control signal;

[0006] The receiving end is used to communicate with the downhole equipment, and the control end is connected to the sending end to transmit control signals;

[0007] The transmitting end includes: a light source whose luminous characteristics conform to the characteristics of a Lambertian point light source, and a multi-stage voltage amplification control module connected to the light source, which is used to control the flickering of the light source according to the control signal;

[0008] The receiving end includes: a photodiode for converting the captured light signal into an electrical signal, a transimpedance amplifier module for amplifying the converted signal, and a signal processing module for recovering the control signal.

[0009] Furthermore, the control terminal is used to:

[0010] Based on LabVIEW as the system control core, it realizes the functions of command generation, communication status display and signal sending;

[0011] Based on the physical connection between the USB-TTL module and the sending end, control instructions are sent through keyboard input and the communication status is displayed in real time.

[0012] Furthermore, in the transmitting end:

[0013] The light source consists of 42 LEDs with a total power of 35W, white light color, a color temperature of 6500K, a luminous efficacy of 120lm / W, and a modulation bandwidth of 375kHz. The LED array is mounted in a rectangular structure on an 80mm x 120mm perforated board.

[0014] Multi-stage voltage amplification control module is used to amplify the control signal through multiple stages to achieve driving capability from low voltage to high voltage, so as to complete high-frequency flicker control and meet the high-power driving requirements of LEDs;

[0015] The transmitting end further includes:

[0016] The signal shaping module is connected to the control terminal and is used to compare the control signal with the reference voltage to eliminate signal distortion during hardware transmission and ensure stable signal output;

[0017] The power module is used to convert 220V AC power into a stable DC power supply to provide power support for the entire sending end.

[0018] Furthermore, in the receiving end:

[0019] The photodiode's response wavelength covers 400 to 1100 nm, the response time is 15 ns, and the dark current is as low as 0.5 pA, making it suitable for mine environments;

[0020] Transimpedance amplifier with a gain of 10^6V / A and a bandwidth of 5MHz to ensure signal integrity;

[0021] The signal processing module is used to receive the amplified signal and perform signal shaping and filtering through an analog-to-digital converter to restore the original control signal.

[0022] The present invention also discloses a downhole equipment communication method based on visible light, which is implemented based on the above-mentioned downhole equipment communication system based on visible light. The method includes:

[0023] The control end generates a control signal and transmits it to the transmitting end. The transmitting end controls the flashing state of the light source based on the control signal to transmit the light signal into the air channel.

[0024] The optical signal is transmitted to the receiving end through line of sight. The optical signal at the receiving end is converted into an electrical signal, amplified, and then processed and demodulated to obtain a demodulated signal.

[0025] Send the demodulated signal to the device.

[0026] Furthermore, the signal processing after the electrical signal is amplified includes: performing a shaping method using a dynamic decision voltage that is adjusted in real time according to the size of the waveform peak voltage, specifically as follows:

[0027] Step 1: Measure the voltage value of the original input signal in real time through the analog-to-digital converter and capture the peak voltage V max , which is the highest voltage of the signal;

[0028] Step 2: Generate a PWM signal. The duty cycle of the PWM signal determines the average voltage of the output signal. The duty cycle is defined as:

[0029] DC=(T n / T)×100%

[0030] Where DC is the duty cycle, T n is the high level duration, T is the total cycle time;

[0031] By adjusting the duty cycle, the average voltage of the output PWM signal is V max / 2;

[0032] Step 3: Smooth the PWM signal through an RC low-pass filter. The RC low-pass filter is used to block high-frequency components above the cutoff frequency and only allow low-frequency components below the cutoff frequency to pass through. The cutoff frequency is expressed as:

[0033] f c =1 / (2πRC)

[0034] Where R is the resistance value and C is the capacitance value;

[0035] Step 4: Set the decision voltage to V max / 2, the signal after RC filtering outputs a DC voltage, which is V max / 2, this DC voltage is the decision voltage used to compare the voltage value of the pre-processed signal;

[0036] If the voltage of the signal is higher than the decision voltage, the signal is judged to be a high level; if the voltage of the signal is lower than the decision voltage, the signal is judged to be a low level;

[0037] Step 5: Implement signal shaping. By comparing the preprocessed signal and the decision voltage, the original input signal is reconstructed into a standard digital signal so that the shaped signal can be restored to a square wave shape.

[0038] The present invention further discloses a downhole device, comprising a device body, which is communicatively connected to a receiving end of the downhole device communication system based on visible light described above to execute instructions.

[0039] The present invention also discloses a method for controlling downhole equipment, comprising:

[0040] Acquire a demodulated signal by using the downhole equipment communication method based on visible light as described above;

[0041] Execute corresponding instructions based on the demodulated signal.

[0042] The above technical solution achieves the dual functions of mine lighting and data communication. By combining OOK modulation and high-power LEDs, it provides uniform illumination while achieving reliable data transmission. The system features a low-power, low-complexity hardware design. It utilizes multi-stage voltage amplification and high-performance PIN photodiodes to improve communication speed and anti-interference capabilities, while ensuring adaptability and stability in harsh environments. Furthermore, the system supports rapid deployment and maintenance, complies with existing mine power supply architectures, and utilizes electromagnetic interference-free visible light communication technology, providing a safe and efficient solution for the intelligent and green development of mines.

[0043] Other beneficial effects of the present invention will be described in detail in the specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 This is a system block diagram of a downhole equipment communication system based on visible light disclosed in an embodiment of the present invention.

[0046] Figure 2 It is a schematic diagram of the radiation range of the lighting system disclosed in the embodiment of the present invention.

[0047] Figure 3 This is a schematic diagram of channel transmission of visible light communication in a mine disclosed in an embodiment of the present invention.

[0048] Figure 4 It is a schematic diagram of the signal transmission process disclosed in an embodiment of the present invention.

[0049] Figure 5 This is a schematic diagram of the simulation of the lighting effect of the square structure disclosed in the embodiment of the present invention.

[0050] Figure 6 It is a schematic diagram of the simulation of the circular structure lighting effect disclosed in an embodiment of the present invention.

[0051] Figure 7 This is a color temperature diagram disclosed in an embodiment of the present invention.

[0052] Figure 8 This is a relative spectral power distribution diagram under different color temperatures disclosed in an embodiment of the present invention.

[0053] Figure 9 This is a diagram of the LED modulation bandwidth disclosed in an embodiment of the present invention.

[0054] Figure 10 This is a diagram of the lighting module architecture disclosed in an embodiment of the present invention.

[0055] Figure 11 This is an illumination simulation diagram disclosed in an embodiment of the present invention.

[0056] Figure 12 This is a waveform diagram of a receiving end response voltage signal disclosed in an embodiment of the present invention.

[0057] Figure 13 This is a signal shaping logic diagram disclosed in an embodiment of the present invention.

[0058] Figure 14 This is a reference voltage waveform diagram disclosed in an embodiment of the present invention.

[0059] Figure 15 It is a demodulated signal waveform diagram disclosed in an embodiment of the present invention.

[0060] Figure 16 It is a waveform diagram of the control signal disclosed in the embodiment of the present invention.

[0061] Figure 17 This is a response waveform diagram under a harsh channel environment disclosed in an embodiment of the present invention.

[0062] Figure 18It is a principle circuit diagram of a low-pass filter disclosed in an embodiment of the present invention.

[0063] Figure 19 This is a demodulation waveform diagram under a harsh channel environment disclosed in an embodiment of the present invention.

[0064] Figure 20 This is a physical picture of the controlled vehicle disclosed in the embodiment of the present invention.

[0065] Figure 21 This is a diagram of an experimental scenario disclosed in an embodiment of the present invention.

[0066] Figure 22 This is a diagram of a bad channel state disclosed in an embodiment of the present invention.

[0067] Figure 23 It is a system architecture diagram disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0068] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0069] The professional terms involved in the embodiments of the present invention are as follows:

[0070] OOK, On-OffKeying, refers to a modulation method;

[0071] LabVIEW refers to a program development environment;

[0072] USB-TTL refers to a commonly used electronic conversion module;

[0073] ADC, Analog-to-Digital Converter, analog-to-digital converter;

[0074] LOS, Line-of-Sight Transmission, line-of-sight transmission;

[0075] NLOS, Non-Line-of-Sight Transmission, non-line-of-sight transmission.

[0076] Example 1

[0077] like Figure 1As shown, the present invention discloses a downhole equipment communication system based on visible light, comprising: a control end for generating a control signal, a transmitting end for sending the optical signal into an air channel, and a receiving end for receiving the optical signal and restoring it into a control signal.

[0078] Among them, the receiving end is used to communicate with the downhole equipment, and the control end is connected to the sending end to transmit control signals.

[0079] The transmitting end includes: a light source whose luminous characteristics conform to the characteristics of a Lambertian point light source, and a multi-stage voltage amplification control module connected to the light source, which is used to control the flickering of the light source according to a control signal.

[0080] The receiving end includes: a photodiode for converting the captured light signal into an electrical signal, a transimpedance amplifier module for amplifying the converted signal, and a signal processing module for recovering the control signal.

[0081] Specifically, this embodiment mainly includes the following steps:

[0082] Step 1: Implementation of the control terminal. The control terminal uses LabVIEW software as the system control core, providing command generation, communication status display, and signal transmission functions. Physically connected to the transmitter via a USB-TTL module, the control terminal can send various control commands via keyboard input and display communication status in real time. If the connection is interrupted, the control terminal can immediately stop signal transmission to prevent misoperation; once the connection is restored, the system automatically restarts. The control terminal's intuitive interface and simple operation make it suitable for the complex working environment of mines.

[0083] Step 2: Implementation of the sender. The sender mainly includes the following submodules:

[0084] The light source module uses a 2W white LED with a color temperature of 6500K, a luminous efficacy of 120lm / W, and a modulation bandwidth of 375kHz. The LED array is mounted in a rectangular structure on an 80mm x 120mm perforated board, providing high illumination uniformity and meeting underground lighting requirements.

[0085] The signal shaping module uses the STM32F103C8T6 microcontroller to compare the control signal with the reference voltage, eliminating signal distortion during hardware transmission and ensuring stable signal output.

[0086] The multi-stage voltage amplifier module achieves driving capability from low voltage (3.3V) to high voltage (19.5V) through multi-stage amplification of the signal. It uses IRF520 MOSFET to complete high-frequency flicker control to meet the high-power LED driving requirements.

[0087] The power module uses the SM-GPA40B-24 industrial control power module to convert 220V AC power into a stable DC power supply, providing efficient and reliable power support for the entire transmitter.

[0088] Step 3: Implementation of the control end. The receiving end design is based on PIN photodiode and transimpedance amplifier to complete the signal capture, amplification and demodulation functions.

[0089] The photodiode module uses LSSPD-1.2PIN photodiode, which has a response wavelength covering 400-1100nm, a response time of 15ns, and a dark current as low as 0.5pA, making it suitable for high dust and high humidity environments in mines.

[0090] The transimpedance amplifier module uses a transimpedance amplifier based on AD825 to convert the weak photocurrent signal into a processable voltage signal with a gain of up to 10^6V / A and a bandwidth of 5MHz to ensure signal integrity.

[0091] In the signal processing module, the microcontroller STM32F103C8T6 receives the amplified signal, completes signal shaping and filtering through the high-resolution ADC module, and restores the original control instructions.

[0092] Step 4: Communication process: When the control end sends a command, the signal is transmitted to the sending end through the USB-TTL module, and after shaping, it controls the high-frequency flashing of the LED; the optical signal is transmitted to the receiving end through the line-of-sight channel (LOS). The photodiode captures the optical signal and converts it into an electrical signal. After amplification by the transimpedance amplifier, the microcontroller completes the signal processing and demodulation, and finally feeds the demodulated signal back to the control system to achieve point-to-point communication.

[0093] Step 5: Environmental Adaptability: The system analyzes the characteristics of the optical signal in the channel and automatically adjusts the signal shaping and demodulation strategies. In good channel environments, simple OOK demodulation is used. In poor channel environments (high dust and high humidity), the system uses dynamic algorithms to optimize signal shaping and filtering to ensure demodulation accuracy.

[0094] Step 6: Experimental verification: the system was installed in a simulated mine environment for testing. When the communication distance was 3.5 meters, the illumination uniformity reached more than 50lx, the data transmission rate reached 19.2Kbps, and the signal error rate was less than 10. ^-6 In high-humidity and high-dust environments, the system was able to maintain stable communication performance by adjusting the demodulation strategy, verifying its reliability and practicality.

[0095] like Figure 2As shown in FIG. , this embodiment illustrates the radiation range of the lighting system. The luminous characteristics of LEDs conform to the Lambertian point light source characteristic, meaning that the light intensity gradually decreases as the angle of incidence increases, reaching its maximum intensity in the vertical direction. Its brightness distribution conforms to the isotropic brightness characteristic, meaning that the brightness distribution remains the same regardless of the direction from which it is viewed, and the light is evenly distributed. Although the light intensity varies with angle, the total radiated power remains constant.

[0096] like Figure 3 As shown in FIG, this embodiment shows a transmission channel diagram. It describes the signal transmission process from the transmitter to the receiver in a visible light communication system, including line-of-sight (LOS) and non-line-of-sight (NLOS) transmission. The transmitter generates an optical signal by controlling the high-frequency flashing of an LED. The optical signal propagates through the air and reaches the receiver via a direct path (LOS) or after reflection (NLOS). The photodiode at the receiver captures the optical signal and converts it into an electrical signal. After amplification by a transimpedance amplifier, it is transmitted to a microcontroller for demodulation and recovery.

[0097] like Figure 4 As shown, this embodiment shows a signal transmission process diagram. It shows the entire communication process from the control end generating the control signal to the receiving end completing the signal recovery. The control end generates a digital signal through the microcontroller and transmits it to the transmitting end. The transmitting end modulates the on and off state of the LED according to the control signal and emits the optical signal into the air channel. The receiving end receives the optical signal through the photodiode and converts it into an electrical signal. After amplification by the transimpedance amplifier, it is transmitted to the microcontroller for filtering, shaping and demodulation, and finally restored to the original control signal. The entire process clearly reflects the full-link operation of the signal from generation, modulation, transmission to demodulation.

[0098] like Figure 5 and Figure 6 As shown in the figure, this embodiment shows the simulation diagram of the lighting effect of square and circular structures. In terms of the lighting module architecture, the difference in lighting effects between square and circular structures is fully considered. Under the same type and number of LED configurations, the lighting effects of the two shapes are simulated using TracePro software.

[0099] like Figure 7 As shown in the figure, this embodiment displays a color temperature diagram. Compared to the 5500K color temperature LEDs commonly used in the market, the 6500K color temperature LEDs selected in this embodiment produce light that is closer to the cool white light of daylight. The color composition also significantly increases the blue light component, resulting in a higher photon density and stronger spectral power. Because blue light has higher energy than red light, it has greater penetration in harsh channel environments, thereby ensuring the stability of communication system transmission.

[0100] like Figure 8 As shown in the figure, this embodiment shows the relative spectral power distribution diagrams under different color temperatures.

[0101] As Figure 9 shown in the figure, this embodiment shows the LED modulation bandwidth diagram. When the lighting module takes into account lighting while realizing fast stroboscopic for information transmission, the modulation bandwidth of the LEDs used largely determines the modulation bandwidth of the visible light communication system. By applying a square wave signal with the same amplitude and duty cycle to both ends of a single LED, changing the frequency of the square wave signal, observing the change process of its light intensity, and conducting a large number of experiments, the data result diagram is obtained.

[0102] As Figure 10 shown in the figure, this embodiment shows the lighting module architecture diagram. This design proposes a 6*7 rectangular architecture as the lighting system architecture, forming a lighting LED with a total voltage of 19.5V, a total current of 1.8A, and a total power of 35W, and installing it in an 80mm*120mm perforated board to ensure heat dissipation during its lighting process.

[0103] As Figure 11 shown in the figure, this embodiment shows the illuminance simulation diagram. This time, the illuminance of the designed lighting module was simulated in the working environment from 2m to 4m. According to the lighting simulation results, when the communication distance is 3.5m, the illuminance is greater than 50lx, meeting the national standard; when the communication distance is 3m, the illuminance is greater than 70lx, which is better than the existing lighting devices in the market.

[0104] As Figure 12 shown in the figure, this embodiment shows the waveform diagram of the received response voltage signal. It can be seen from the figure that there is indeed an obvious tailing phenomenon in its received waveform, which is consistent with the above theoretical analysis. The level sizes of its response low levels are not uniform, and the size of the response high level is about 2.2V. Such signals cannot be recognized by the receiving end controller when input.

[0105] As Figure 13 shown in the figure, this embodiment shows the signal shaping logic diagram. In this embodiment, STM32F103C8T6 is used as the controller for shaping. By using the ADC function in this controller, the demodulated analog signal is changed into a digital signal V1 that can be mathematically compared. By introducing a decision voltage V2, the demodulated signal voltage V1 read each time is compared with the decision voltage V2. When V1<V2, the pin outputs a low level; when V1>V2, the pin outputs a high level.

[0106] As Figure 14 shown in the figure, this embodiment shows the reference voltage waveform diagram. The DC signal in the figure is the magnitude of the extracted reference voltage. It can be seen that when taking 50% of the peak voltage, the reference voltage passes through all the mutation points in the demodulated signal.

[0107] As Figure 15 As shown in FIG, this embodiment shows a demodulated signal waveform diagram. The demodulated signal is a square wave signal, the demodulated signal peak voltage is 3.3V, and the low voltage signal is 0V, which meets the TTL signal demodulation standard.

[0108] like Figure 16 As shown in FIG, this embodiment shows the waveform of the control signal. The demodulated signal variation trend well replicates the control end signal, and the duration of the signal is roughly the same as the duration of the control end signal, which is consistent with the time error of the system demodulation.

[0109] like Figure 17 As shown in FIG, this embodiment shows the response waveform diagram under a bad channel environment. Compared with a good channel environment, the shape of the receiving waveform under a bad channel environment does not change, but the peak voltage is reduced.

[0110] like Figure 18 As shown in FIG, this embodiment shows the principle circuit diagram of a low-pass filter. Low-pass filters are generally divided into analog low-pass filters and digital low-pass filters. Analog filters are generally composed of resistors, capacitors, or inductors. A common low-pass filter is an RC low-pass filter, which consists of a resistor and a capacitor.

[0111] like Figure 19 As shown in FIG, this embodiment shows the demodulation waveform diagram under a harsh channel environment. The waveform of the demodulated signal is the same as the transmitted signal waveform, and the peak voltage of the demodulated signal is 3.3V and the minimum voltage is 0V, which conforms to the characteristics of the TTL waveform and can be effectively read in the input system.

[0112] like Figure 20 As shown, this embodiment shows a real-life image of the controlled vehicle. To simulate the actual working environment of a mine, the controlled object verified in this embodiment is a remote-controlled intelligent vehicle, simulating an underground mine vehicle. A transmission scenario with a communication distance of 3.5 meters was established in dark conditions.

[0113] like Figure 21 As shown in the figure, this embodiment demonstrates an experimental scenario. During the experiment, when the control end sent commands at a rate of 19.2 Kbps, the robot quickly recognized the control information and took corresponding actions. The robot also maintained effective communication within the lighting module's extreme illumination range. Measurements showed that the entire system's latency was approximately 10 microseconds, which is within an acceptable range.

[0114] like Figure 22 As shown in Figure 1, this embodiment shows a diagram of a poor channel state. To simulate underground mine communication, this embodiment experiment built a 3.5m*1m*1m closed communication environment. Water mist and smoke were added to the scene to simulate the high dust and high water vapor conditions during underground mine operations.

[0115] Example 2

[0116] Based on the content disclosed in Example 1, this example further illustrates the present invention.

[0117] The method for constructing a downhole equipment communication system based on visible light disclosed in this embodiment is as follows:

[0118] (1) Overall design of underground visible light communication system

[0119] First, the characteristics of the underground mine environment were analyzed and corresponding design indicators were proposed. Next, a model of the underground visible light communication system was constructed. The system was analyzed theoretically and an LED lighting model, modulation method, and system model suitable for the underground environment were selected. Finally, corresponding design solutions were proposed for each component of the underground visible light communication system. This part provided theoretical support for subsequent designs.

[0120] (1.1) Analyze requirements and environmental characteristics. In mine environments, tunnels are typically narrow, long, and enclosed. High humidity and dust levels pose severe challenges to signal transmission. The system must meet the dual requirements of mine lighting and communication, with a communication range of at least 3.5 meters and uniform illumination coverage without blind spots. Furthermore, the system must be portable to accommodate dynamic deployments and achieve stable, highly reliable communication even in harsh channel conditions.

[0121] (1.2) Theoretical Model and Technology Selection: Based on optical characteristics, a light source and channel model based on the Lambertian model was constructed to distinguish between line-of-sight (LOS) and non-line-of-sight (NLOS) transmission characteristics. Regarding modulation technology, after comparing OOK, FSK, and PSK, OOK modulation was selected due to its simplicity and efficiency, which is well-suited to the complex environment of mines. Furthermore, a system model was proposed based on theoretical analysis, emphasizing the improvement of transmission reliability by increasing the incident optical power and optimizing the receiver design.

[0122] (1.3) System Architecture and Module Design: Design the system architecture encompassing the control, transmitter, and receiver, clarifying the functions of each module. The control side uses LabVIEW for signal generation and interface communication. The transmitter utilizes high-power LEDs for modulation and illumination, while also employing a multi-stage voltage amplifier circuit to enhance drive capability. The receiver utilizes a PIN photodiode, a transimpedance amplifier, and a microcontroller for signal reception, shaping, and demodulation. Ultimately, define clear requirements for the system's functionality and performance, including communication rate, signal reliability, and hardware adaptability.

[0123] The LED model is specifically constructed as follows: the luminous characteristics of the luminous LED conform to the Lambertian point light source characteristics, that is, the light intensity gradually decreases as the output angle increases, and the light intensity is maximum in the vertical direction, as shown in formula (1). Its brightness distribution conforms to the isotropic brightness characteristics, that is, the brightness distribution is the same regardless of the direction from which it is viewed, and the light is evenly distributed; although the light intensity changes with the angle, its total radiant power is constant.

[0124] I θ =I0*cos(θ) (1)

[0125] Where: I0——maximum radiation intensity in the normal direction, lux;

[0126] θ——the angle between the radiation direction and the normal, degrees.

[0127] In practical applications, the LEDs of the lighting module are regularly distributed, and the position of each LED can be determined by r l Position vector representation, n l is the normal vector of the luminous surface, and its mathematical model can be expressed as:

[0128] S={r l ,n l ,m,FOV} (2)

[0129] Where: FOV - Field of View (FOV) of the LED;

[0130] m——Mode parameter of luminous directionality.

[0131]

[0132] That is, the light intensity distribution of the LED light source can be expressed as:

[0133]

[0134] Then the incident light power of LED is:

[0135]

[0136] Where: γ——small solid angle, degree;

[0137] S r ——Effective receiving area of ​​the receiver, m 2 ;

[0138] d – distance from LED to receiver, m.

[0139] In the transmission channel of d=3.5m, the overall radiation range of the LED is as follows Figure 2As shown, its radiation range can be expressed as:

[0140] X=tanα*3.5*2 (6)

[0141] Where: α is half of the field of view (FOV) of the LED lighting system, degrees;

[0142] X——horizontal radiation distance, m.

[0143] like Figure 3 The channel transmission diagram of visible light communication in mines is shown in the figure. When the signal is transmitted to the receiving end, due to the difference in relative position, the transmission path is divided into line-of-sight transmission (LOS) and non-line-of-sight transmission (NLOS). The signal transmission process is as follows: Figure 4 As shown, the control signal is transmitted to the sending control circuit via the microcontroller to control the light-emitting LED to flash on and off. The receiving end PD receives the light intensity signal sent by the LED and transmits it to the microcontroller via the receiving circuit to complete the entire signal transmission. The process can be expressed as:

[0144]

[0145] Where: R——photodiode response rate;

[0146] X(t)——LED emission intensity, lux;

[0147] h(t)——unit impulse response of the channel;

[0148] N(t) – Gaussian noise in the channel.

[0149] The unit impulse response is composed of the unit impulse responses of n light-emitting LEDs and m PDs. It is essentially the sum of the unit impulse responses of n*m single LEDs and single PDs. That is, the unit impulse response h(t) can be expressed as:

[0150]

[0151] Where: h (0) (t) —Unit impulse response generated in the LOS channel;

[0152] It represents the unit impulse response after k reflections in the NLOS channel.

[0153] In a mine communication system, the communication distance is much greater than the size of the PD receiving surface. In addition, due to the uneven inner wall of the mine, the absorption and reflection of light are severe. The impulse response of the system is mainly contributed by the LOS channel. In this embodiment, only the LOS channel is considered, that is:

[0154]

[0155] Where: A R ——Effective receiving area of ​​PD, m 2 ;

[0156] ——The angle between the PD receiving line and the normal, degrees.

[0157] The PD response is given by the following formula:

[0158] I r =R I *P in (10)

[0159] Where: I r ——Response current, A;

[0160] R I ——PD responsivity: when the wavelength of the incident light is constant, the responsivity is a constant value.

[0161] According to the above PD response formula, if we want to enhance the system's response current, we need to increase the incident light power under the LOS channel, that is, increase the system's unit impulse response h(t), to ensure the system's In order to ensure the reliability of system transmission, in point-to-point communication, the incident optical power should be increased as much as possible, the system response current should be increased, and the stable transmission of the system should be guaranteed.

[0162] (2) Design of OOK modulation LED lighting communication module suitable for underground environment.

[0163] This embodiment mainly considers the lighting and communication aspects to design the underground LED lighting communication module, and selects and designs the lighting module from the aspects of lighting characteristics, modulation bandwidth, etc.; to address the control signal interference problem in the communication process, a signal shaping module design is proposed; to address the coupling problem of the lighting control circuit and the communication circuit, a multi-stage voltage amplification control circuit design is proposed; to address the energy supply problems in lighting and communication, a circuit design that meets the energy supply needs is proposed.

[0164] In terms of lighting module architecture, the difference in lighting effects between square and round shapes was fully considered. Under the same type and number of LED configurations, the lighting effects of the two shapes were simulated using TracePro software. Figure 5 and Figure 6 shown.

[0165] The results show that the maximum illuminance of the square structure is 1.0444e-005lx and the minimum is 3.6018e-018lx; the maximum illuminance of the circular structure is 1.1259e-004lx and the minimum is 1.2418e-017lx. The absolute difference in illuminance of the square structure is significantly smaller than that of the circular structure, indicating that in practical applications, the square structure has a more uniform lighting effect, is less likely to form a spot effect, and has a higher light source utilization rate.

[0166] See also Figure 7 As shown in the color temperature diagram, the color of LED light with a higher color temperature is more inclined to cool white light, similar to daylight. In the color composition, the blue light component increases significantly, thereby increasing the photon density and spectral power. The simulation results of its spectral power are shown in Figure 7 As shown in Figure 2, blue light has higher energy than red light and is more penetrable in harsh channel environments, which helps ensure the stability of communication system transmission.

[0167] The lighting module needs to achieve fast strobing for information transmission while providing illumination. Therefore, the modulation bandwidth of the LED used largely determines the modulation bandwidth of the visible light communication system. By applying a square wave signal with the same amplitude and duty cycle to both ends of a single LED and changing the frequency of the square wave signal, the change in its light intensity can be observed. Through a large number of experiments, the data results collected are as follows Figure 9 shown.

[0168] The LED modulation bandwidth is usually defined by the 3dB frequency of the LED, that is, the half-power point. From the results, it can be seen that the frequency corresponding to the 3dB frequency point of the LED used is 750KHz. Since this embodiment adopts OOK modulation, the period of sending a single 0 or 1 signal is 750KHz, so in theory the modulation bandwidth of the LED is 375KHz (which should be the frequency of half a period, that is, half of 750KHz), which meets the rate requirement for control signal transmission under normal circumstances.

[0169] To ensure the reliability of the communication system, this embodiment uses Fangpu 2W bright white LED as the lighting source. This LED has excellent characteristics in terms of color temperature, luminous efficiency, and maximum allowable junction temperature. The main parameters are shown in Table 1. To integrate the advantages of the above architecture, this design proposes a 6*7 rectangular architecture as the lighting system architecture, forming a lighting LED with a total voltage of 19.5V, a total current of 1.8A, and a total power of 35W. It is installed in an 80mm*120mm perforated board to ensure heat dissipation during the lighting process. Figure 10 shown.

[0170] Table 1 Main parameters of lighting LED

[0171]

[0172] In mine lighting, in order to ensure the safety of underground operations, the requirements for lighting illumination vary according to different working environments. Based on these requirements and the specific parameters and architecture of LEDs, the LED illumination is simulated, such as Figure 11 shown.

[0173] This embodiment simulates the illumination of the designed lighting module in an environment of 2m to 4m. According to the lighting simulation results, when the communication distance is 3.5m, the illumination is greater than 50lx, meeting the national standard; when the communication distance is 3m, the illumination is greater than 70lx, which is better than existing lighting devices on the market.

[0174] (3) Design of environment-adaptive demodulation module based on OOK modulation.

[0175] First, the core components of the demodulation module are introduced and selected, and the appropriate device models are given according to the design specifications. Secondly, the OOK demodulation waveform characteristics in a good channel environment are analyzed, and a corresponding demodulation scheme is proposed. Finally, the demodulation waveform in a bad environment is analyzed, and an adaptive demodulation scheme is proposed.

[0176] When the transmitter outputs a control command, the lighting module adjusts the LED's power supply voltage according to the control command to achieve high-frequency flashing of the LED. According to the volt-ampere characteristics of the LED, the law of how the current across the LED changes with voltage can be obtained:

[0177]

[0178] Where: I LED ——The current across the LED, A;

[0179] I s ——LED reverse saturation current, A;

[0180] V——voltage across the LED, V;

[0181] n——LED ideal factor;

[0182] V T ——Thermovoltage, V.

[0183] According to formula (11), the current change of LED is proportional to the voltage change of LED. The current increases with the increase of voltage. When the voltage increases to the maximum thermal voltage, the current of LED tends to be stable at I s At this time, the emitted light power of a single LED can be expressed as:

[0184]

[0185] The transmission power P of the lighting module s for:

[0186]

[0187] Where: n is the total number of LEDs that make up the lighting module.

[0188] From formula (12), it can be seen that the emission power of the LED is related to the LED's electro-optical conversion efficiency η, which is usually in the range of 10% to 50%. The specific value is related to the LED material and structure.

[0189] At this time, the number of photons generated by the lighting module is N s :

[0190]

[0191] Where: E——single photon energy, KJ;

[0192] h——Planck constant;

[0193] λ——LED center wavelength, nm.

[0194] The channel environment is filled with photon signals emitted by the transmitter lighting module. In a good channel environment, the concentration of dust and water mist in the air is at a low level, and the impact on the communication system can be ignored.

[0195] At the receiving end, it is known that the light intensity distribution characteristics of the transmitting LED obey the Lambertian model. The light is evenly divergent in free space, and at a distance h, the distribution of its photons can be approximated to spherical diffusion, resulting in an area of ​​4πh 2 , and the received optical power density at this distance is I r :

[0196] I r =(εN s ×E) / (4πh 2 ) (15)

[0197] Where: εN s ——The number of photons received at this distance, ε is a constant between 0 and 1.

[0198] It is known that the effective receiving area of ​​the receiving end is S r , then at this distance, the received power of the photodiode is P r :

[0199] P r =I r ×S r =S r ×(εN s ×E) / (4πh 2 ) (16)

[0200] The response current of the photodiode can be obtained from Equation (16). After passing through a transimpedance amplifier, the final response signal can be obtained.

[0201] During the entire communication process, due to the high frequency of the control signal sent, the LED is in a high-frequency switching state, and the electron transition state inside its PN junction is unstable. As a result, within a very short time after the LED is turned off, there are still a small number of electrons in the transition state, that is, the LED still emits weak light. This phenomenon is called the "afterglow effect" of the LED. Due to the existence of this effect, when the 0 control signal is sent, there are still a part of photons N in the channel s , resulting in the photodiode being unable to instantaneously reach the 0-level state and having a large tail.

[0202] According to the bandwidth parameters of the photodiode, due to the charge storage effect inside the photodiode, when the light source stops irradiating, the charges in the depletion layer and the minority carrier region need a long time to be reset. Therefore, the fall time T d is often greater than the rise time T u .

[0203] According to the above theory and selection, a visible light communication system was built to conduct a physical experiment with a communication distance of 3.5 m. The waveform at the receiving end is as Figure 12 shown. It can be seen that there is indeed an obvious tailing phenomenon in its received waveform, which is consistent with the above theoretical analysis. The level sizes of its response low level are not uniform, and the peak voltage of the response signal is approximately 2.2 V. Such signals cannot be recognized by the receiving end controller when input.

[0204] Based on the above analysis, it is proposed to add a decision voltage for signal shaping. The overall idea is Figure 13 shown. In this embodiment, STM32F103C8T6 is used as the controller for shaping. Using the ADC function inside this controller, the demodulated analog signal is changed into a digital signal V1 that can be mathematically compared. By introducing a decision voltage V2, the demodulated signal voltage V1 read each time is compared with the decision voltage V2. When V1 < V2, the pin outputs a low level; when V1 > V2, the pin outputs a high level.

[0205] The setting of the decision voltage V2 will be an important factor affecting the demodulation effect. The value of the decision voltage should be reasonably selected so that it can effectively distinguish the high level and the low level of the signal, thereby ensuring the integrity of the signal. In addition, the signal period after demodulation according to the decision voltage should be consistent with the signal period sent by the control end.

[0206] Figure 12The peak voltage of the response signal shown is approximately 2.2V. When the decision voltage V2 is half of the peak voltage, it passes through all the mutation points of the response waveform and contains all the information in the signal; and the corresponding duration is approximately equal to half a signal cycle, which meets the error condition of the demodulated signal.

[0207] According to the above scheme, the reference voltage of the demodulated signal is taken out as Figure 14 shown.

[0208] The demodulated signal at this decision voltage is as follows Figure 15 The system control terminal sends a signal as shown. Figure 16 shown.

[0209] See also Figure 15 , the demodulated signal is a square wave signal, the demodulated signal peak voltage is 3.3V, the low voltage signal is 0V, which meets the TTL signal demodulation standard. Figure 16 In comparison, the demodulated signal change trend replicates the control end signal very well, and the duration of its signal is roughly the same as the duration of the control end signal, which is consistent with the time error of system demodulation.

[0210] The proposed demodulation signal analysis and adaptive demodulation scheme for harsh channel environments specifically addresses the following: Under normal circumstances, when optical signals propagate through a channel, the dust and water vapor concentrations in the air are low and their volume is small, making the impact of these particles on optical signal propagation negligible. However, during underground mining operations, drilling, cutting, and grinding cause the ore to break down, filling the air with large quantities of tiny water vapor and dust particles, maintaining high concentrations.

[0211] In visible light communications, optical signals can collide with opaque particles and refract in translucent water vapor molecules as the channel environment changes. This reduces the number of optical signals reaching the PD and increases the propagation distance. The attenuation characteristics of optical signals show that the energy of optical signals decays exponentially with increasing propagation distance, resulting in an exponential decay in the received light intensity at the receiving end:

[0212] P r =P s ×e -αl (17)

[0213] Where:

[0214] α - attenuation coefficient, which indicates the degree of attenuation of the signal when propagating through the channel;

[0215] l is the distance the optical signal travels to reach the PD, in meters.

[0216] The influence of dust particles in the air on optical signals is mainly manifested in the scattering and absorption effects on optical signals:

[0217] 1. Scattering effect

[0218] Scattering refers to the change in the propagation direction of a light signal caused by its interaction with dust particles during propagation. For larger particles in the channel, the main types of scattering that occur are Rayleigh scattering and Mie scattering.

[0219] 2. Absorption effect

[0220] Dust particles not only scatter light but also absorb some of it. This is especially true for certain dust particles with absorptive properties, such as coal dust and organic dust. These particles convert the absorbed photon energy into heat, resulting in photon energy loss. The strength of this absorption effect is often influenced by the chemical composition, morphology, and surface characteristics of the particles.

[0221] According to the above analysis, the attenuation effect of particulate dust on photons is affected by its concentration and particle size. In the same spatial range, the dust concentration ρ dust The higher the attenuation coefficient α dust The bigger it is.

[0222] α dust =K×ρ dust (18)

[0223] Where: K is a constant related to the characteristics of dust particles.

[0224] Water vapor in the air usually exists in the form of water vapor. Although its concentration is lower than that of dust, it still has a significant impact on the propagation of visible light communication in a high-humidity channel environment. In long-distance communication and short-wavelength optical communication, there is no phenomenon in water vapor that photons cannot penetrate, and the attenuation of the channel is mainly manifested as absorption.

[0225] The absorption effect is mainly manifested in the interaction between water molecules and photons, absorbing the energy of penetrating photons and converting them into heat energy, resulting in signal attenuation. In this process, the magnitude of the absorption effect is related to the relative humidity. The higher the relative humidity, the stronger the absorption effect.

[0226] α water =N×ρ water (19)

[0227] Where: α water ——Attenuation coefficient caused by water molecule absorption;

[0228] N – coefficient related to the absorption characteristics of water molecules;

[0229] ρ water——Relative humidity of water molecules.

[0230] In a harsh channel environment with high humidity and high dust, the receiving power at the receiving end can be expressed as:

[0231]

[0232] To summarize the above analysis, in a harsh channel environment, when photons propagate, they are attenuated by dust and water molecules in the channel, resulting in lower photon energy, which is manifested as lower received optical power at the receiving end. It can be concluded from formula (16) that under the same communication distance, the harsh channel environment affects the number of photons reaching the photodiode during each strobe, which is manifested as a smaller response voltage compared to that in an excellent channel environment.

[0233] In this embodiment, the communication distance is 3.5m. Even if the photon is absorbed by the photodiode after multiple reflections and refractions, the distance it travels is l≈3.5m, and the time it takes is in the nanosecond level, which can be ignored. This makes the stroboscopic phenomenon of the optical signal remain the same as that in a good channel, ensuring that the shape of the signal does not change.

[0234] To summarize the above conclusions, compared with a good channel environment, the shape of the received waveform in a bad channel environment does not change, but the peak voltage will decrease.

[0235] According to the above theory and selection, a physical 3.5m communication system was built, and dust and a small amount of water mist were mixed into the channel. The received waveform was as follows Figure 17 shown.

[0236] Analysis of the received waveform shows that the peak voltage of the response waveform is 1.5V. When the same control instruction is sent, the waveform shape does not change significantly, which is consistent with the theoretical analysis.

[0237] Experimental results show that this scheme is effective in shaping this type of waveform. However, when applied to the demodulation waveform in a harsh channel environment, its fixed decision voltage is no longer suitable for the peak voltage of this waveform. Therefore, the research focus should be on designing a decision voltage that can change in real time according to the peak voltage of the decision voltage to ensure the signal shaping effect.

[0238] This embodiment uses the controller STM32F103C8T6 to read the peak voltage V of the signal max size, and according to V max By changing the duty cycle of the output pulse modulation signal and combining it with an RC low-pass filter, a decision voltage signal of 50% of the peak voltage is output for signal shaping.

[0239] Pulse Width Modulation (PWM) is a technique for adjusting the average power or voltage of a signal by adjusting the pulse width (i.e., the duration of the high level). PWM signals are typically square waves. Their fundamental characteristic is that the frequency remains constant, while the average output voltage is varied by varying the duration of the high level. Its key characteristics are frequency and duty cycle.

[0240] 1. Frequency

[0241] Frequency f refers to the number of cycles of the PWM signal, that is, the number of complete cycles of the PWM signal per second, and the unit is Hz; period T refers to the time required for the PWM signal to go from the beginning of one cycle to the end of the next cycle, and the unit is S. The relationship between the two is:

[0242] f=1 / T (21) 2. Duty cycle

[0243] Duty Cycle (DC) refers to the duration of the high level of the PWM signal in a complete cycle. n The proportion of the entire cycle, usually expressed as a percentage, ranging from 0% to 100%.

[0244] DC=(T n / T)×100% (22)

[0245] PWM signals play an important role in many fields, especially in controlling and regulating output power. By adjusting the duty cycle of the PWM signal, analog signal-like control can be achieved. The principle formula is:

[0246] V out =D×V o (twenty three)

[0247] Where: V out ——output voltage, V;

[0248] D——Duty cycle of PWM signal;

[0249] V o ——Peak voltage of the microcontroller, V.

[0250] In the STM32 microcontroller, the input voltage V is converted by the built-in 12-bit ADC. in The principle formula of its output voltage becomes:

[0251] V out =V in / 4096×V o (twenty four)

[0252] A PWM signal can be considered a signal consisting of a DC component and multiple high-frequency components. The DC component, determined by the duty cycle, is the desired output signal. The high-frequency components, consisting of the PWM frequency and harmonics, need to be filtered out. By utilizing the RC attenuation characteristics of high-frequency signals, the high-frequency portion of the PWM signal is filtered out, preserving the DC component.

[0253] A low-pass filter is an electronic circuit that allows low-frequency signals to pass through and suppresses high-frequency signals. Its basic function is to pass frequencies below a certain cutoff frequency f. c That is, when the frequency of the original input signal is lower than the cutoff frequency, it can pass through with its intensity and form maintained; when the frequency of the original input signal is higher than the cutoff frequency, the energy of the high-frequency signal is absorbed by the capacitor and attenuated under the impedance of the capacitor, and the degree of attenuation is proportional to the frequency. The original input signal and the preprocessed signal involved in this embodiment actually refer to the representation of the same physical signal at different processing stages. In essence, they are the same signal. Specifically, the signal is an electrical signal received and amplified from the visible light communication system.

[0254] Low-pass filters are usually divided into analog low-pass filters and digital low-pass filters. Analog filters are usually composed of resistors, capacitors or inductors. The most common low-pass filter is the RC low-pass filter, which consists of a resistor and a capacitor. Its principle circuit is as follows: Figure 18 As shown:

[0255] Cutoff frequency f c It is the key to determine the performance of the filter. The cut-off frequency is determined by determining the specific values ​​of the resistance and capacitance in the circuit. The principle formula is:

[0256] f c =1 / (2πRC) (25)

[0257] Where R is the resistance value and C is the capacitance value;

[0258] In summary, in this embodiment, the STM32 pin is used to read the input analog signal, and the peak voltage V of the original input signal is determined by formula (24): max The duty cycle of the output PWM wave signal is determined by formula (22), and the original input signal and output signal are connected according to the principle diagram of the low-pass filter to obtain the judgment DC signal that changes with the peak voltage of the original input signal.

[0259] According to the above theory and selection, a physical experiment is built, and the final demodulated signal is as follows Figure 19 shown.

[0260] From the experimental results, it can be seen that the waveform of the demodulated signal is the same as the waveform of the transmitted signal, and the peak voltage of the demodulated signal is 3.3V and the minimum voltage is 0V, which conforms to the characteristics of the TTL waveform and can be effectively read in the input system.

[0261] (4) System verification. Through physical verification of the above-mentioned design contents and combined with the design indicators, verify whether the designed system meets the requirements;

[0262] The system verification under the excellent channel environment is to simulate the formal working environment under the mine. The controlled object verified in this embodiment is a remote control intelligent car. Figure 20 As shown in the figure, a mine vehicle is simulated. A transmission scenario with a communication distance of 3.5m is built under dark conditions. Figure 21 The remote control smart car can realize the actions of "forward", "backward", "turn left" and "turn right" through different command contents. When the control end sends the corresponding command content, the car can complete the specified action.

[0263] During the experiment, when the control terminal sent commands at a rate of 19.2Kbps, the robot quickly recognized the control information and responded accordingly. Even within the lighting module's extreme illumination range, the robot maintained effective communication. Measurements showed that the system's latency was approximately 10 microseconds, which is within an acceptable range.

[0264] The system verification in the harsh channel environment is to simulate the communication state in the mine. In this embodiment, a closed communication environment of 3.5m*1m*1m is built. Water mist and smoke are added to the scene to simulate the high dust and high water vapor state in the mine operation process. Figure 22 Perform the above verification again.

[0265] During the experiment, the system continued to transmit control signals at the same communication distance and rate, and the controlled vehicle successfully completed the corresponding instructions. The measured communication delay was approximately 17.5 microseconds, which is within an acceptable range.

[0266] Example 3

[0267] This embodiment discloses a downhole equipment communication method based on visible light. The method is implemented based on the downhole equipment communication system based on visible light disclosed in the above embodiment. The method includes:

[0268] The control end generates a control signal and transmits it to the transmitting end. The transmitting end controls the flashing state of the light source based on the control signal to transmit the light signal into the air channel.

[0269] The optical signal is transmitted to the receiving end through line of sight. The optical signal at the receiving end is converted into an electrical signal, amplified, and then processed and demodulated to obtain a demodulated signal.

[0270] Send the demodulated signal to the device.

[0271] There are two possible channel environments during underground mine production: in the early stages of operation, the channel between the transmitter and receiver is in a relatively stable state, that is, there is no high water vapor or high dust in the channel; in the middle and late stages of operation, due to the characteristics of the operation process, there is a large amount of dust and water vapor in the channel, which makes the channel environment relatively harsh. This paper constructs a 3.5-meter communication system under the conditions of simulating a harsh channel environment, and adds dust and a small amount of water mist to the channel for experimental verification. Figure 22 shown.

[0272] The voltage decision method works well when shaping the demodulated signal waveform in a good channel environment. However, when applied to waveform demodulation in a bad channel environment, the single threshold voltage decision method is no longer suitable for the peak voltage of the waveform in a bad channel environment due to its fixed decision voltage value. Therefore, in this embodiment, a dynamic decision voltage is provided that can be adjusted in real time according to the peak voltage of the waveform to ensure the shaping effect of the signal. Figure 23 The system architecture diagram of the embodiment is as follows:

[0273] Step 1: Read the peak voltage V max ,The receiving end signal is captured by the photodiode and converted into an electrical signal, which will be affected by environmental noise and ,transmission characteristics, resulting in inconsistent high and low level fluctuations of the signal.

[0274] The analog-to-digital converter (ADC) built into the STM32F103C8T6 microcontroller can measure the voltage value of the original input signal in real time. By detecting the voltage change of the received signal, the system captures its peak voltage V max , which is the highest voltage of the signal.

[0275] Step 2: Dynamically adjust the duty cycle of the pulse modulation signal. The STM32F103C8T6 generates a pulse width modulation (PWM) signal. The duty cycle of the PWM signal determines the average voltage value of the output signal. The duty cycle is defined as:

[0276] DC=(T n / T)×100% (26)

[0277] Among them, T n is the high level duration, and T is the total cycle time.

[0278] To generate a dynamic decision voltage, the duty cycle of the PWM signal needs to be consistent with the measured peak voltage V maxBy adjusting the duty cycle, the average voltage of the output PWM signal can be made V max / 2, which is half of the peak voltage.

[0279] Step 3: RC low-pass filter to smooth the DC signal. The PWM signal is essentially a square wave signal with rapid switching between high and low levels. To generate a stable DC voltage, an RC low-pass filter is required to smooth the PWM signal.

[0280] The function of RC low-pass filter is to block high-frequency components and only allow low-frequency components to pass. Its cut-off frequency f c for:

[0281] f c =1 / (2πRC) (27)

[0282] Where R is the resistance value and C is the capacitance value;

[0283] Step 4: Set the decision voltage to V max / 2, the signal after RC filtering outputs a DC voltage, which is V max / 2. This is the dynamic decision voltage. The decision voltage is used to compare the voltage value of the pre-processed signal:

[0284]

[0285] Step 5: Implement signal shaping. Utilizing the STM32's logic judgment function, the original input signal is reconstructed into a standard digital signal (high or low) by comparing the preprocessed signal with the judgment voltage. The shaped signal restores the ideal square wave shape and eliminates the tailing and low-level drift caused by signal distortion.

[0286] Example 4

[0287] This embodiment discloses a downhole device and a control method. The downhole device includes a device body, which is communicatively connected to a receiving end of the downhole device communication system based on visible light disclosed in the above embodiment to execute instructions.

[0288] Correspondingly, the control method of the downhole equipment disclosed in this embodiment includes: acquiring a demodulated signal through the downhole equipment communication method based on visible light disclosed in the above embodiment; and executing corresponding instructions based on the demodulated signal.

[0289] The above description is merely a preferred embodiment of the present disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also encompass other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the above-mentioned inventive concept. For example, a technical solution formed by mutually replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure.

[0290] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A downhole equipment communication method based on visible light, characterized in that: The method includes: The control end generates a control signal and transmits it to the transmitting end. The transmitting end controls the flashing state of the light source based on the control signal to transmit the light signal into the air channel. The optical signal is transmitted to the receiving end through line of sight. The optical signal at the receiving end is converted into an electrical signal, amplified, and then processed and demodulated to obtain a demodulated signal. Send the demodulated signal to the device end; The signal processing after the electrical signal is amplified includes: a shaping method using a dynamic decision voltage that is adjusted in real time according to the peak voltage of the waveform, as follows: Step 1: Measure the voltage value of the original input signal in real time through the analog-to-digital converter and capture the peak voltage V max , which is the highest voltage of the signal; Step 2: Generate a PWM signal. The duty cycle of the PWM signal determines the average voltage of the output signal. The duty cycle is defined as: DC=(T n / T)×100% Where DC is the duty cycle, T n is the high level duration, T is the total cycle time; By adjusting the duty cycle, the average voltage of the output PWM signal is V max / 2; Step 3: Smooth the PWM signal through an RC low-pass filter. The RC low-pass filter is used to block high-frequency components above the cutoff frequency and only allow low-frequency components below the cutoff frequency to pass through. The cutoff frequency is expressed as: in c =1 / (2πRC) Where R is the resistance value and C is the capacitance value; Step 4: Set the decision voltage to V max / 2, the signal after RC filtering outputs a DC voltage, which is V max / 2, this DC voltage is the decision voltage used to compare the voltage value of the pre-processed signal; If the voltage of the preprocessing signal is higher than the decision voltage, the signal is judged to be a high level; if the voltage of the preprocessing signal is lower than the decision voltage, the signal is judged to be a low level; Step 5: Implement signal shaping. By comparing the preprocessed signal and the decision voltage, the original input signal is reconstructed into a standard digital signal so that the shaped signal can be restored to a square wave shape.

2. A downhole equipment communication system based on visible light, used to execute the downhole equipment communication method based on visible light according to claim 1, characterized in that: include: A control end for generating a control signal, a transmitting end for transmitting an optical signal into an air channel, and a receiving end for receiving the optical signal and restoring it into a control signal; The receiving end is used to communicate with the downhole equipment, and the control end is connected to the sending end to transmit control signals; The transmitting end includes: a light source whose luminous characteristics conform to the characteristics of a Lambertian point light source, and a multi-stage voltage amplification control module connected to the light source, which is used to control the flashing of the light source according to the control signal; The receiving end includes: a photodiode for converting the captured light signal into an electrical signal, a transimpedance amplifier module for amplifying the converted signal, and a signal processing module for recovering the control signal.

3. The downhole equipment communication system based on visible light according to claim 2, characterized in that: The control terminal is used for: Based on LabVIEW as the system control core, it realizes the functions of command generation, communication status display and signal sending; Based on the physical connection between the USB-TTL module and the sending end, control instructions are sent through keyboard input and the communication status is displayed in real time.

4. The downhole equipment communication system based on visible light according to claim 2, characterized in that: In the sending end: The light source consists of 42 LEDs with a total power of 35W, white light color, a color temperature of 6500K, a luminous efficacy of 120lm / W, and a modulation bandwidth of 375kHz. The LED array is mounted in a rectangular structure on an 80mm x 120mm perforated board. Multi-stage voltage amplification control module is used to amplify the control signal through multiple stages to achieve driving capability from low voltage to high voltage, so as to complete high-frequency flicker control and meet the high-power driving requirements of LEDs; The transmitting end further includes: The signal shaping module is connected to the control terminal and is used to compare the control signal with the reference voltage to eliminate signal distortion during hardware transmission and ensure stable signal output; The power module is used to convert 220V AC power into a stable DC power supply to provide power support for the entire sending end.

5. The downhole equipment communication system based on visible light according to claim 2, characterized in that: In the receiving end: The photodiode's response wavelength covers 400 to 1100 nm, the response time is 15 ns, and the dark current is as low as 0.5 pA, making it suitable for mine environments; Transimpedance amplifier with a gain of 10^6V / A and a bandwidth of 5MHz to ensure signal integrity; The signal processing module is used to receive the amplified signal and perform signal shaping and filtering through an analog-to-digital converter to restore the original control signal.

6. A downhole device, characterized in that: The device comprises a device body, which is communicatively connected to a receiving end in the downhole equipment communication system based on visible light according to any one of claims 2 to 5 to execute instructions.

7. A method for controlling downhole equipment, characterized in that: include: Obtaining a demodulated signal by the downhole equipment communication method based on visible light according to claim 1; Execute corresponding instructions based on the demodulated signal.

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