Pulsed vcsel-based ultra-low-power methane wireless monitoring system and monitoring method

Abstract

A pulsed VCSEL-based ultra-low-power methane wireless monitoring system and a method. A pulse-driven VCSEL methane detection module (1) comprises an MCU control module (11), a pulse drive circuit (12) having an automatic sleep and wake-up function, a VCSEL light source (13), a photodetector (14), a gas absorption cell optical path (15), a temperature and pressure sensor (16), and embedded firmware (17). The monitoring system automatically wakes up a methane node detection device corresponding to the MCU control module (11), receives the ambient temperature acquired by the temperature and pressure sensor (16) at the current moment, controls, for different temperatures, the gas absorption cell optical path (15) to use different absorption peak spectra to perform methane concentration measurement, determines whether a methane concentration is within a preset safety range, if so, switches the pulse-driven VCSEL methane detection module (1) to a sleep mode until a preset sleep time is reached, automatically wakes up the pulse-driven VCSEL methane detection module (1) and re-performs concentration measurement, and if the measured concentration value is consistently within the preset safety range, controls the pulse-driven VCSEL methane detection module (1) to continuously and repeatedly alternate between a "wake-up" mode and a "sleep" mode; and if the methane concentration exceeds the preset safety range, activates an acousto-optic alarm module (2) to give an alarm.

Description

A pulsed VCSEL-based ultra-low power methane wireless monitoring system and method

[0001] Cross-reference to related applications

[0002] This invention claims priority to Chinese Patent Application No. 202410908727.3, filed on July 8, 2024, entitled "A Wireless Monitoring System and Method for Methane Based on Pulsed VCSEL", the entire contents of which are incorporated herein by reference and constitute a part of this invention for all purposes. Technical Field

[0003] This invention belongs to the field of methane or natural gas leak safety monitoring, and particularly relates to a wireless methane monitoring system and method based on pulsed VCSEL ultra-low power consumption. Background Technology

[0004] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0005] The existence of cross-interference issues in methane alarms based on electrochemical or catalytic combustion makes the advantages of tunable diode laser absorption spectroscopy (TDLAS) technology even more prominent.

[0006] However, in many practical applications, it is necessary to use batteries to drive methane detection alarm devices, while requiring methane concentration measurement frequencies of once every few seconds or tens of seconds, and the ability for the methane sensor to be used for several years or even nearly ten years without replacing the battery module. Due to the high power consumption of these sensors, such application requirements are difficult to meet for general TDLAS methane sensors that use DFB lasers as light sources. Therefore, the application requirements mentioned above pose a difficult technical challenge to existing related technologies.

[0007] Summary of the Invention

[0008] To address at least one of the technical problems mentioned above, this invention provides a low-power wireless methane monitoring system and method based on pulsed VCSELs. This system can measure methane concentration every few seconds or tens of seconds and ensure that the methane node detection device does not need to replace its power supply battery during use for several years or even ten years.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention provides a wireless methane monitoring system based on pulsed VCSEL ultra-low power consumption, comprising a plurality of battery-powered pulsed VCSEL methane detection modules, wherein each pulsed VCSEL methane detection module includes an MCU control module and a gas absorption cell optical path.

[0011] The MCU control module is configured to automatically wake up the VCSEL methane detection module corresponding to the MCU control module when the methane wireless monitoring system is running normally, receive the current ambient temperature, and receive the methane concentration value obtained by the gas absorption cell optical path using different absorption peak spectra for different ambient temperatures.

[0012] Determine if the methane concentration is within the preset safety range. If so, switch the VCSEL methane detection module to sleep mode until the preset sleep time is reached, then automatically wake up the methane node detection device and re-detect the methane concentration. If the measured methane concentration value is always within the preset safety range, control the VCSEL methane detection module to continuously alternate between the "wake-up" and "sleep" modes.

[0013] If the methane concentration exceeds the preset safety range, an alarm message will be issued.

[0014] In one embodiment, the pulse-driven VCSEL methane detection module further includes a VCSEL light source and a photodetector. The optical path of the gas absorption cell includes a COB circuit board, a collimating curved surface mirror, a focusing curved surface mirror, and an elliptical curved surface mirror. The VCSEL light source and the photodetector are respectively fixed at preset positions on the COB circuit board. The light outlet of the VCSEL light source is located at the focal point of the collimating curved surface mirror, and the photosensitive surface of the photodetector is located at the focal point of the focusing curved surface mirror. The VCSEL light source and the photodetector are respectively connected to the MCU control module. The light beam emitted by the VCSEL light source is reflected by the collimating curved surface mirror to form a collimated beam parallel to the COB plane. After being reflected by the elliptical curved surface mirror, the beam enters the focusing curved surface mirror. After being reflected by the focusing curved surface mirror, the incident beam is focused on the photosensitive surface of the photodetector. The photodetector converts the optical signal into an electrical signal and sends it to the MCU control module.

[0015] In one implementation, the VCSEL light source and photodetector are replaced with TO-can devices.

[0016] In one embodiment, the collimating curved mirror and the focusing curved mirror are made of a rotating parabolic mirror surface.

[0017] In one implementation, the system further includes a monitoring terminal, which is connected to the methane node detection device via a wireless gateway;

[0018] The monitoring terminal is configured to receive, summarize, store and display the current ambient temperature value, gas concentration value, alarm status and alarm location information of each methane node detection device at preset time intervals.

[0019] In one implementation, the monitoring system further includes a wireless data communication module and a battery drive module, which are electrically connected to the MCU control module. The data communication module uploads methane concentration data to the monitoring terminal, and the battery drive module supplies power to the methane node detection device.

[0020] As one implementation, the monitoring system also includes an audible and visual alarm module. The pulse-driven VCSEL methane detection module is connected to the audible and visual alarm module. If the methane concentration exceeds the preset safety range, the audible and visual alarm module is activated to issue an alarm message.

[0021] In one implementation, the battery drive module uses a D-type battery with model number CR34615 and a capacity of 19Ah.

[0022] As one implementation, the pulse-driven VCSEL methane detection module also includes embedded firmware, which is written into the non-volatile memory of the MCU control module. After the gas absorption cell optical path detects methane concentration using different absorption peak spectra, the embedded firmware in the MCU control module automatically finds the absorption peak and calculates the concentration value.

[0023] To address the aforementioned problems, a second aspect of the present invention provides a method for a pulsed VCSEL-based ultra-low power methane wireless monitoring system according to the first aspect, comprising the following steps:

[0024] Obtain the current ambient temperature, and for different ambient temperatures, use different absorption peak spectra to detect and deduce the methane concentration value based on the calibration value;

[0025] Determine if the methane concentration is within the preset safety range. If so, switch the VCSEL methane detection module to sleep mode until the preset sleep time is reached, then automatically wake up the methane node detection device and re-detect the methane concentration. If the measured methane concentration value is always within the preset safety range, control the VCSEL methane detection module to continuously alternate between the "wake-up" and "sleep" modes.

[0026] If the methane concentration exceeds the preset safety range, an alarm message will be issued.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. Since the methane node detection device of the present invention uses VCSEL as a light source, the methane node detection device can adjust the scanning current of the laser according to different ambient temperatures and use different methane absorption peak spectra for detection, so that the laser can work in different temperature ranges. This not only expands the working temperature range of the sensor, but also reduces the power consumption of TEC temperature control because the VCSEL laser does not need to use TEC.

[0029] 2. To protect the VCSEL laser from the impact of pulsed current, the MCU control module employs a slow-start and slow-shutdown VCSEL current drive scheme when automatically waking up the methane node detection device. Through the MCU control module's pulse drive circuit, which allows for automatic sleep and wake-up, the methane node detection device can periodically monitor the methane gas concentration. Since the methane node detection device is in a shut-off state during the interval between two detections, its operating power consumption is further reduced.

[0030] 3. Since the control module of each methane node detection device can independently detect and determine the gas concentration value at that node, it can ensure that the methane concentration value at that node is always kept within a safe range. If it is not, the control alarm module of the methane node detection device will sound an alarm at that node, ensuring that the gas concentration at that node is detected and alarmed in a timely manner. The control module also uploads the collected data and judgment results to the background monitoring center, and displays the collected data, alarm status, and alarm location at the background monitoring center. In this way, the monitoring center can monitor and manage these application scenarios around the clock and throughout the entire process to prevent gas leaks and ensure the safety of life and property.

[0031] 4. Because the methane node detection device provided by this invention can be battery-powered and uses wireless communication to transmit the detected concentration value, these methane node detection devices can be installed in various application locations without power supply or where it is not easy to connect to a power supply. Then, a wireless node aggregation gateway is used to connect several methane node detection devices into a larger methane wireless detection network and connect it to the background monitoring center. In this way, the background monitoring center can conduct long-term monitoring and management of different application scenarios such as natural gas pipelines, buildings with gas supply, and residential buildings, and can promptly monitor and alarm natural gas leakage events to ensure the safety of life and property.

[0032] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0034] Figure 1 is a schematic diagram of a wireless monitoring system based on a pulsed VCSEL ultra-low power methane sensor provided in an embodiment of the present invention;

[0035] Figure 2 is a functional structural diagram of the methane node detection device provided in an embodiment of the present invention;

[0036] Figure 3 is a schematic diagram of the functional structure of the methane module provided in an embodiment of the present invention;

[0037] Figure 4 is a schematic diagram of the optical path of a lensless gas absorption cell with a curved reflective surface provided in an embodiment of the present invention;

[0038] Figure 5 is a schematic diagram of the wireless monitoring method of the pulsed VCSEL ultra-low power methane sensor provided in an embodiment of the present invention.

[0039] Figure 6 is a schematic diagram of the optical path of the gas absorption cell using a TO-can laser and detector provided in an embodiment of the present invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] In this invention, terms such as "connected" and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0044] Example 1

[0045] This embodiment provides an ultra-low power methane wireless monitoring system based on pulsed VCSEL, including:

[0046] As shown in Figure 1, the system includes several battery-powered methane node detection devices and a background monitoring terminal.

[0047] The aforementioned methane node detection devices can be installed in various application locations without power supply or where it is difficult to connect to power lines. The methane node detection devices can be connected into a larger methane detection network using a wireless node aggregation gateway. This gateway is connected to the background monitoring center, which summarizes, stores, and displays the current ambient temperature, gas concentration, alarm status, and alarm location of each methane node detection device. This enables long-term monitoring and management of these methane node detection devices placed in different application scenarios, such as natural gas pipelines, buildings with gas supply, and residential buildings. It also enables timely monitoring and alarming of natural gas leaks to ensure the safety of life and property.

[0048] As shown in Figure 2, the methane node detection device includes a pulse-driven VCSEL methane detection module 1, an audible and visual alarm module 2, a wireless data communication module 3, and a battery-driven module 4.

[0049] The wireless data communication module 3, the battery drive module 4, and the pulse-driven VCSEL methane detection module 1 are electrically connected. The methane concentration data is uploaded to the monitoring terminal through the wireless data communication module 3, and the methane node detection device is powered through the battery drive module 4.

[0050] In this embodiment, the wireless communication module can be a 3G, 4G, GPRS, or WIFI wireless communication module. The driving battery is a CR34615 type D battery with a capacity of 19Ah.

[0051] As shown in Figure 3, the pulse-driven VCSEL methane detection module 1 includes an MCU control module 11, a pulse drive circuit 12 that can automatically sleep and wake up, a VCSEL light source 13, a photodetector 14, a lensless gas absorption cell optical path 15 composed of curved reflective surfaces, a temperature and pressure sensor 16, and embedded firmware 17 that automatically finds absorption peaks and calculates concentration values.

[0052] It should be noted that the VCSEL methane detection module used in this embodiment utilizes the low power consumption, tunability, and narrow linewidth characteristics of VCSELs. By selecting specific absorption spectra of different analytes within different temperature ranges, interference from other gas spectra can be eliminated, and the operating temperature range of the VCSEL methane detection module can be broadened. Furthermore, the VCSEL methane detection module of this embodiment exhibits high accuracy within a certain temperature range (typically -30℃ to 70℃).

[0053] As shown in Figure 4, the lensless gas absorption cell optical path 15 composed of curved reflective surfaces includes a COB (Chip-on-board) circuit board 151, a VCSEL chip 152 disposed on the VCSEL light source 13 and a detector chip 153 disposed on the photodetector 14, a collimating curved reflector 154, a focusing curved reflector 155 and an elliptic reflector 156; the two curved reflective surfaces are made of parabolic reflectors.

[0054] The VCSEL chip 152 and detector chip 153 are respectively fixed at preset positions on the COB circuit board 151. The light output port of the VCSEL chip 152 is located at the focal point of the collimating curved reflector 154, and the photosensitive surface of the detector chip 153 is located at the focal point of the focusing curved reflector 155. Then, the pads of the VCSEL chip 152 and the detector chip 153 are connected to the circuit on the COB through gold wires, so that the VCSEL chip is connected to the automatic sleep and wake-up pulse drive circuit 12 controlled by the MCU control module, while the detector chip 153 is connected to the MCU control module through an automatic gain circuit and an ADC sampling circuit.

[0055] The collimating curved surface mirror 154 emitted by the VCSEL chip 152 reflects a collimated beam parallel to the COB plane. After being reflected by the elliptical curved surface mirror, the beam enters the focusing curved surface mirror 155 of the detector 153. The beam is focused onto the detector chip 153 by the mirror reflection. The detector chip 153 converts the optical signal into an electrical signal, which is then amplified and converted by the ADC and input to the MCU control module.

[0056] Since no lenses are used in the optical path design of this lensless gas absorption cell, that is, no collimating lens is used in front of the laser and no focusing lens is used in front of the detector, the interference background noise introduced by the mirror reflection of these lenses can be effectively avoided, thereby increasing the detection sensitivity.

[0057] As shown in Figure 5, when the methane wireless monitoring system is operating normally, the MCU control module in each methane node detection device automatically wakes up the device. The MCU control module detects the ambient temperature using a temperature sensor. For different ambient temperatures, the VCSEL laser uses different absorption peaks for detection, and the embedded firmware that automatically finds the absorption peak and calculates the concentration value is used to retrieve the measured concentration. After the VCSEL laser enters a stable working state, it samples and measures the methane concentration in the environment where the methane node detection device is located. The MCU control module then judges the methane concentration value collected at the location of the methane node detection device.

[0058] If the concentration value detected by the methane node detection device is within the preset safety range, the MCU control module switches the methane node detection device to sleep mode. After the preset sleep time ends, the MCU control module automatically wakes up the methane node detection device and repeats the methane concentration detection. If the measured concentration value is always within the preset safety range, the methane node detection device will alternate between the "wake-up" and "sleep" modes. At the same time, after a preset time interval, such as every few hours or 24 hours, the MCU control module will activate the wireless communication module to upload the collected data to the background monitoring center so that the monitoring center can understand and record the operating status of the methane node detection device.

[0059] If the methane concentration detected by the methane node detection device exceeds the preset alarm value, the control module of the methane node detection device will activate the audible and visual alarm module to provide on-site alarm prompts at the node, and upload the collected methane concentration data to the background monitoring center through its wireless communication module, or activate linkage devices such as electric ball valves to perform corresponding actions to shut down the gas pipeline.

[0060] Because the control modules of each methane node detection device can independently detect and determine the gas concentration value at that node, it can ensure that the methane concentration value at that node remains within a safe range. If it is outside the safe range, the control alarm module of the methane node detection device will sound an alarm at that node, ensuring that the gas concentration at that node is detected and alarmed in a timely manner. The control module also uploads the collected data and judgment results to the background monitoring center, where the collected data, alarm status, and alarm location are displayed. In this way, the monitoring center can monitor and manage these application scenarios around the clock and throughout the entire process, preventing gas leaks and ensuring the safety of life and property.

[0061] Since the methane node detection device of the present invention uses VCSEL as a light source, the methane node detection device can adjust the scanning current of the laser according to different ambient temperatures and use different methane absorption peak spectra for detection, so that the laser can work in different temperature ranges. This not only expands the sensor's operating temperature range, but also reduces the power consumption of TEC temperature control because the VCSEL laser does not require the use of TEC.

[0062] To protect the VCSEL laser from the impact of pulsed current, the MCU control module employs a slow-start and slow-shutdown VCSEL current drive scheme when automatically waking up the methane node detection device. Through the MCU control module's pulse drive circuit, which allows for automatic sleep and wake-up, the methane node detection device can periodically monitor methane gas concentration. Since the methane node detection device is in a shut-off state during the intervals between detections, its operating power consumption is further reduced.

[0063] Example 2

[0064] This embodiment provides a battery-powered ultra-low-power wireless methane monitoring system based on a pulse-driven VCSEL. In addition to the schemes shown in Figures 1 to 5, Figure 6 provides a detailed description. As shown in Figure 6, the VCSEL laser 13 and photodetector 14 are replaced by a TO-can device for detection. The TO-can device includes a VCSEL laser 21 with a collimating lens, a COB circuit board 151, a detector 22 with a focusing lens, and an elliptic surface reflector 156. Its specific working principle is the same as that of the gas absorption cell optical path 15.

[0065] The advantage is that different types or manufacturers of VCSEL lasers or detectors can be selected to realize the function of the methane wireless monitoring system. The disadvantage is that the measurement accuracy is reduced due to the interference noise introduced by the reflection of the lens surface because of the lens used in the optical path.

[0066] Example 3

[0067] This embodiment provides a method for a pulsed VCSEL-based ultra-low power methane wireless monitoring system as described in Embodiment 1 or Embodiment 2, comprising the following steps:

[0068] The MCU control module detects the current ambient temperature, uses different absorption peak spectra for different ambient temperatures, and derives the methane concentration value based on the calibration value.

[0069] Determine if the methane concentration value is within the preset safety range. If so, control the methane node detection device to switch to sleep mode until the preset sleep time is reached, then automatically wake up the methane node detection device and re-detect the methane concentration. If the measured methane concentration value is always within the preset safety range, control the methane node detection device to continuously alternate between the "wake up" and "sleep" modes.

[0070] If the methane concentration exceeds the preset safety range, an alarm message will be issued.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-power wireless methane monitoring system based on pulsed VCSEL, characterized in that, It includes several battery-powered pulse-driven VCSEL methane detection modules, each of which includes an MCU control module and a gas absorption cell optical path. The MCU control module is configured to automatically wake up the VCSEL methane detection module corresponding to the MCU control module when the methane wireless monitoring system is running normally, receive the current ambient temperature, and receive the methane concentration value obtained by the gas absorption cell optical path using different absorption peak spectra for different ambient temperatures. Determine if the methane concentration is within the preset safety range. If so, switch the VCSEL methane detection module to sleep mode until the preset sleep time is reached, then automatically wake up the methane node detection device and re-detect the methane concentration. If the measured methane concentration value is always within the preset safety range, control the VCSEL methane detection module to continuously alternate between the "wake-up" and "sleep" modes. If the methane concentration exceeds the preset safety range, an alarm message will be issued.

2. The ultra-low power methane wireless monitoring system based on pulsed VCSEL as described in claim 1, characterized in that, The pulse-driven VCSEL methane detection module also includes a VCSEL light source and a photodetector. The optical path of the gas absorption cell includes a COB circuit board, a collimating curved surface mirror, a focusing curved surface mirror, and an elliptical curved surface mirror. The VCSEL light source and the photodetector are respectively fixed at preset positions on the COB circuit board. The light outlet of the VCSEL light source is located at the focal point of the collimating curved surface mirror, and the photosensitive surface of the photodetector is located at the focal point of the focusing curved surface mirror. The VCSEL light source and the photodetector are respectively connected to the MCU control module. The light beam emitted by the VCSEL light source is reflected by the collimating curved surface mirror to form a collimated beam parallel to the COB plane. After being reflected by the elliptical curved surface mirror, the beam enters the focusing curved surface mirror. After being reflected by the focusing curved surface mirror, the incident beam is focused on the photosensitive surface of the photodetector. The photodetector converts the optical signal into an electrical signal and sends it to the MCU control module.

3. The ultra-low power methane wireless monitoring system based on pulsed VCSEL as described in claim 2, characterized in that, The VCSEL light source and photodetector are replaced by TO-can devices.

4. The ultra-low power methane wireless monitoring system based on pulsed VCSEL as described in claim 2, characterized in that, The collimating curved surface mirror and the focusing curved surface mirror are made of a rotating parabolic mirror surface.

5. The ultra-low power methane wireless monitoring system based on pulsed VCSEL as described in claim 1, characterized in that, The system also includes a monitoring terminal, which is connected to the methane node detection device via a wireless gateway. The monitoring terminal is configured to receive, summarize, store and display the current ambient temperature value, gas concentration value, alarm status and alarm location information of each methane node detection device at preset time intervals.

6. The ultra-low power methane wireless monitoring system based on pulsed VCSEL as described in claim 1, characterized in that, The monitoring system also includes a wireless data communication module and a battery drive module. The wireless data communication module and the battery drive module are electrically connected to the MCU control module. The data communication module uploads methane concentration data to the monitoring terminal, and the battery drive module supplies power to the methane node detection device.

7. The ultra-low power methane wireless monitoring system based on pulsed VCSEL as described in claim 1, characterized in that, The monitoring system also includes an audible and visual alarm module. The pulse-driven VCSEL methane detection module is connected to the audible and visual alarm module. If the methane concentration exceeds the preset safety range, the audible and visual alarm module is activated to issue an alarm message.

8. The ultra-low power methane wireless monitoring system based on pulsed VCSEL as described in claim 1, characterized in that, The battery drive module uses a CR34615 type D battery with a capacity of 19Ah.

9. The ultra-low power methane wireless monitoring system based on pulsed VCSEL as described in claim 1, characterized in that, The pulse-driven VCSEL methane detection module also includes embedded firmware, which is written into the non-volatile memory of the MCU control module. After the gas absorption cell optical path detects methane concentration using different absorption peak spectra, the embedded firmware in the MCU control module automatically finds the absorption peak and calculates the concentration value.

10. A method for a pulsed VCSEL-based ultra-low power methane wireless monitoring system according to any one of claims 1-9, characterized in that, Includes the following steps: Obtain the current ambient temperature, and for different ambient temperatures, use different absorption peak spectra to detect and deduce the methane concentration value based on the calibration value; Determine if the methane concentration is within the preset safety range. If so, switch the VCSEL methane detection module to sleep mode until the preset sleep time is reached, then automatically wake up the methane node detection device and re-detect the methane concentration. If the measured methane concentration value is always within the preset safety range, control the VCSEL methane detection module to continuously alternate between the "wake-up" and "sleep" modes. If the methane concentration exceeds the preset safety range, an alarm message will be issued.

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