Soil trace gas emission rate in-situ measurement device and method based on three-axis mechanical arm

Abstract

The invention discloses a soil trace gas emission rate in-situ measurement device and method based on a three-axis mechanical arm, and relates to the technical field of soil trace gas flux measurement, the soil trace gas emission rate in-situ measurement device comprises a gas chamber, the gas chamber comprises a cubic bearing platform and a cylindrical gas chamber main body, and the cylindrical gas chamber main body is installed on the lower surface of the cubic bearing platform; the cylindrical air chamber main body is communicated with the cubic bearing platform, a control module is mounted on the upper surface of the cubic bearing platform, and a three-axis mechanical arm is arranged in the cubic bearing platform; according to the device, by constructing a spatial dynamic detection matrix and a dynamic weighted average algorithm, the technical problems that in open type dynamic gas chamber method monitoring, steady-state criteria are not clear, and spatial heterogeneity affects precision are effectively solved, and the accuracy and reliability of soil trace gas flux monitoring are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of soil trace gas flux measurement technology, specifically to an in-situ measurement device and method for soil trace gas emission rate based on a three-axis robotic arm. Background Technology

[0002] Trace gases in soil are trace gases produced and released into the atmosphere by soil microbial metabolism, plant root respiration, or physicochemical processes. They mainly include carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Although these gases are present in low concentrations in the atmosphere, they have a strong greenhouse effect and ecological sensitivity, significantly impacting global climate change, atmospheric chemistry, and ecosystem carbon and nitrogen cycles. Measuring soil trace gas emission rates not only helps assess greenhouse gas emission levels in terrestrial ecosystems but also reveals the regulatory roles of agricultural management, land-use change, and climate factors on soil carbon and nitrogen processes. Therefore, accurately measuring soil trace gas emission rates is crucial for assessing terrestrial ecosystem carbon and nitrogen cycles, studying greenhouse gas emission sources, developing agricultural emission reduction measures, and supporting climate model parameterization.

[0003] Currently, the mainstream methods for measuring soil trace gas emission rates are the gas chamber method and the micrometeorological method. Each method has its advantages and disadvantages, with the gas chamber method being the most widely used. The gas chamber method is divided into the static gas chamber method and the dynamic gas chamber method. The dynamic gas chamber method is further divided into the closed gas chamber method and the open dynamic gas chamber method. The static gas chamber method and the closed dynamic gas chamber method calculate the soil trace gas flux by utilizing the change in trace gas concentration within the gas chamber over time. The open dynamic gas chamber method, on the other hand, calculates the soil trace gas flux by using the difference in trace gas concentration between the gas chamber inlet and outlet, combined with flow rate parameters.

[0004] When the open dynamic gas chamber method uses a steady-state model to calculate the flux, it is necessary to first confirm that the gas chamber has reached a steady state. Nowadays, most scholars judge whether the gas chamber has reached a steady state by the magnitude of the concentration change at the outlet. If the rate of change of the target gas concentration at the outlet tends to be stable, it is considered that the gas chamber has reached a steady state.

[0005] Previous open-type dynamic gas chamber monitoring methods have the following technical drawbacks: First, the steady-state criterion relies on sampling at a single location. When the gas mixture in the chamber is insufficient or there is a temperature gradient, the concentration distribution exhibits significant spatial heterogeneity, leading to the risk of misjudgment of steady-state conditions. Second, the measurement method uses concentration data from a single or a small number of measurement points to calculate flux. In non-steady-state environments, factors such as inlet turbulence or soil porosity cause spatial heterogeneity in the trace gas concentration within the chamber space, resulting in a large error between the flux data measured under non-steady-state conditions and the actual flux value.

[0006] To address the aforementioned shortcomings, this invention will design an in-situ measurement device and method for soil trace gas emission rates that can be measured at multiple points inside a gas chamber. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to propose an in-situ measurement device and method for soil trace gas emission rate based on a three-axis robotic arm. This device effectively solves the technical problems of unclear steady-state criteria and spatial heterogeneity affecting accuracy in open dynamic gas chamber monitoring by constructing a spatial dynamic detection matrix and a dynamic weighted average algorithm, and significantly improves the accuracy and reliability of soil trace gas flux monitoring.

[0008] To achieve the above objectives, the present invention provides the following technical solution: an in-situ measurement device for soil trace gas emission rate based on a three-axis robotic arm, comprising a gas chamber, the gas chamber comprising a cubic support platform and a cylindrical gas chamber body, the cylindrical gas chamber body being mounted on the lower surface of the cubic support platform, the cylindrical gas chamber body being interconnected with the cubic support platform, a control module being mounted on the upper surface of the cubic support platform, and a three-axis robotic arm being disposed in the cubic support platform.

[0009] Preferably, the control module consists of a main controller, a power supply module, and a motor driver. The main controller controls the robotic arm to perform three-dimensional movements on the cubic support platform and the cylindrical air chamber body. The power supply module is responsible for supplying power to the entire device.

[0010] Preferably, the three-axis robotic arm includes a slide rail, a slide table, and a synchronous belt. The slide rail includes a first slide rail, a second slide rail, a third slide rail, and a fourth slide rail. The bottom sides of the slide table are slidably mounted on the slide rail. The bottom of the slide table is fixedly mounted on the synchronous belt. A stepper motor is fixedly mounted on one end of the slide rail. The stepper motor is used to drive the synchronous belt to move along the slide rail. One end of the synchronous belt is connected to the middle of the slide rail, and the other end of the synchronous belt is driven to the stepper motor drive shaft.

[0011] Preferably, the first, second, third, and fourth slide rails are each uniformly provided with a slide table and a synchronous belt. The first and second slide rails are symmetrically installed on both sides of the bottom of the cubic support platform. One end of the third slide rail is fixedly installed on the slide table of the first slide rail, and the other end of the third slide rail is fixedly installed on the slide table of the second slide rail. The fourth slide rail is fixedly installed on the slide table of the third slide rail. A target gas sensor is fixedly installed on the slide table of the fourth slide rail at the end away from the third slide rail. The target gas sensor is disposed in the cylindrical gas chamber body.

[0012] Preferably, the cylindrical air chamber body has symmetrically installed air inlets on its inner wall, and the cylindrical air chamber body has air outlets and air inlets respectively opened on its inner wall. The guide plate is installed on the cubic support platform near the air outlets and air inlets.

[0013] An in-situ measurement method for soil trace gas emission rates based on a triaxial robotic arm, preferably comprising:

[0014] S1. Install the air chamber base in the area to be measured, install the cubic support platform and the cylindrical air chamber body on the base and seal them, install the air pump and air flow monitoring sensor on the air outlet and air inlet side of the air chamber respectively, and set the parameters of the air flow monitoring sensors at the air outlet and air inlet to be the same.

[0015] S2, Sensors are installed on the three-axis robotic arm, and the control module controls the movement of the three-axis robotic arm to obtain the rate of change of trace gas concentration at multiple points inside the gas chamber;

[0016] S3. Fifteen measurement points are set in the cylindrical gas chamber. When the average rate of change of each point in the cylindrical gas chamber is lower than the set threshold, the system is determined to have reached a steady state. When the average rate of change of each point in the gas chamber is higher than the set threshold, a dynamic weighted average algorithm based on spatial weight allocation is adopted. Combined with the flux calculation model under unsteady state, the soil trace gas flux is finally obtained.

[0017] Preferably, the feature is that when each point in the gas chamber in S3 reaches a steady state, the soil trace gas flux is calculated using the flux calculation formula under steady-state conditions combined with the gas concentrations obtained from the inlet and outlet. The specific calculation formula is as follows:

[0018]

[0019] Where A is the soil area covering the gas chamber, F represents the flux of the target trace gas inside the gas chamber, Q represents the gas flow rate at the inlet and outlet, and C... in and C out These represent the concentrations of the target trace gas at the inlet and outlet, respectively.

[0020] The formula for calculating soil trace fluxes under unsteady conditions described in S3 is as follows:

[0021]

[0022] In the formula, Let V be the rate of change of trace gas concentration at each measurement point, ignoring the differences in volume distribution inside the gas chamber, meaning that all measurement points share the same volume V, and i represents the measurement point location.

[0023] As a preferred embodiment, the dynamic weight calculation formula in the dynamic weighted average algorithm described in S3 is as follows:

[0024]

[0025] In the formula, j represents the number of the 15 measurement points; C represents the trace gas concentration; and e represents the natural constant. The gradient modulus is the value of each measurement point. The gradient modulus characterizes the spatial variation intensity of trace gas concentration around the measurement point, and the calculation formula is as follows:

[0026]

[0027] In this process, the gradient between the four vertices of the same horizontal plane in the cylindrical air chamber is calculated only with respect to the two adjacent points; the steps described above yield Fi and ω. i The weighted average is calculated using the following formula:

[0028]

[0029] In the formula, F avg This represents the soil trace gas flux when the gas chamber is in a non-steady-state condition.

[0030] As a preferred approach, the flux calculation model is based on the law of conservation of component mass, which states that in a closed or open system, the mass of a component cannot be created or destroyed; it can only be changed through inflows and outflows at the system boundary or through generation and consumption within the system. The rate of change is expressed as: (Inflow - Outflow + Generation - Consumption).

[0031] ΔM=M in -M out +M pro -M con

[0032] In the formula, M in M represents the rate of change in inflow; out M represents the rate of change in outflow; pro Indicates the rate of change; M con Indicates the rate of change in consumption;

[0033] When measuring using the gas chamber method, no chemical reaction occurs inside the gas chamber with trace gases, therefore M con Item and M pro With the term set to zero, we obtain the following formula:

[0034] ΔM=M in -M out

[0035] Based on the above law, the gas flux inside an open flow chamber can be expressed by the formula:

[0036]

[0037] Where V represents the volume of the air chamber, and V is a constant, the above formula can be simplified to:

[0038]

[0039] In the formula, V represents the volume of the air chamber. This represents the rate of change of the target gas concentration inside the gas chamber, where A is the soil area covering the gas chamber, and Q represents the gas flow rate C at the inlet and outlet. in and C out These represent the concentrations of the target gas at the inlet and outlet, respectively, and R represents the rate at which trace gases emitted from the soil enter the gas chamber.

[0040] The formula for the trace gas flux F released per unit area of ​​soil can be expressed as:

[0041]

[0042] Where A represents the area of ​​contact between the bottom of the gas chamber and the soil. Based on the simplified formula, the specific formula for calculating the soil trace gas flux in an open dynamic gas chamber is as follows:

[0043]

[0044] Compared with existing technologies, the in-situ measurement device and method for soil trace gas emission rate based on a three-axis robotic arm provided by the present invention has the following advantages:

[0045] 1. This device effectively solves the technical problems of unclear steady-state criteria and spatial heterogeneity affecting accuracy in open dynamic gas chamber monitoring by constructing a spatial dynamic detection matrix and a dynamic weighted average algorithm, and significantly improves the accuracy and reliability of soil trace gas flux monitoring.

[0046] 2. This invention uses a three-axis robotic arm equipped with a gas sensor to perform path scanning within the gas chamber, acquiring concentration change rate distribution data at different locations within the gas chamber space. This improves the accuracy of gas chamber status judgment, effectively eliminates spatial representativeness errors caused by traditional single-point measurements, and more accurately calculates soil trace gas flux. Furthermore, this invention eliminates the need to place multiple gas sensors inside the gas chamber to acquire gas concentration distribution data, significantly saving sensor costs. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the in-situ measurement method for soil trace gas emission rate based on a three-axis robotic arm according to the present invention.

[0048] Figure 2 This is a schematic diagram of the three-dimensional structure of the present invention;

[0049] Figure 3 This is a schematic diagram showing the connection relationship of the main structure of the cylindrical air chamber of the present invention;

[0050] Figure 4 This is a schematic diagram showing the distribution of measurement points and the movement trajectory of the robotic arm in this invention.

[0051] In the picture:

[0052] 1. Cube-shaped support platform; 2. Cylindrical air chamber main body;

[0053] 11. Control module; 12. Wiring hole; 13. Slide rail; 14. Slide table; 15. Synchronous belt; 16. Stepper motor;

[0054] 21. Deflector; 22. Air outlet; 23. Air inlet; 24. Target gas sensor. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0056] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0057] Example 1, please refer to Figures 1 to 4 As shown:

[0058] To address the problems mentioned in the technical solutions, this application provides an in-situ measurement device for soil trace gas emission rates based on a three-axis robotic arm, comprising a gas chamber. The gas chamber includes a cubic support platform 1 and a cylindrical gas chamber body 2. The cylindrical gas chamber body 2 is mounted on the lower surface of the cubic support platform 1 and is interconnected with the cubic support platform 1. A control module 11 is mounted on the upper surface of the cubic support platform 1, and a three-axis robotic arm is disposed in the cubic support platform 1.

[0059] The control module 11 consists of a main controller, a power supply module, and a motor driver. The main controller controls the robotic arm to perform three-dimensional movements on the cubic support platform 1 and the cylindrical air chamber body 2. The power supply module is responsible for supplying power to the entire device.

[0060] The three-axis robotic arm includes a slide rail 13, a slide table 14, and a synchronous belt 15. The slide rail 13 includes a first slide rail, a second slide rail, a third slide rail, and a fourth slide rail. The slide table 14 is slidably mounted on the slide rail 13 on both sides of its bottom end. The bottom of the slide table 14 is fixedly mounted on the synchronous belt 15. A stepper motor 16 is fixedly mounted on one end of the slide rail 13. The stepper motor 16 is used to drive the synchronous belt 15 to move on the slide rail 13. One end of the synchronous belt 15 is connected to the middle of the slide rail 13, and the other end of the synchronous belt 15 is driven on the drive shaft of the stepper motor 16.

[0061] The effective stroke of the three-axis robotic arm is 240mm×240mm×200mm, and the slide length is 60mm.

[0062] The first, second, third, and fourth slide rails are evenly provided with slide tables 14 and synchronous belts 15. The first and second slide rails are symmetrically installed on both sides of the bottom of the cubic support platform 1. One end of the third slide rail is fixedly installed on the slide table 14 in the first slide rail, and the other end of the third slide rail is fixedly installed on the slide table 14 of the second slide rail. The fourth slide rail is fixedly installed on the slide table 14 of the third slide rail. A target gas sensor 24 is fixedly installed on the slide table 14 of the fourth slide rail at the end away from the third slide rail. The target gas sensor 24 is located in the cylindrical gas chamber body 2.

[0063] 2-The inner wall is symmetrically equipped with air inlets 23. The inner wall of the cylindrical air chamber body 2 is respectively provided with air outlets 22 and air inlets 23. The guide plate 21 is installed on the cubic support platform 1 near the air outlets 22 and air inlets 23.

[0064] The gas chamber is made of stainless steel and consists of a cylindrical gas chamber body 2, 300mm high and 300mm in diameter, and a top cubic support platform 1, 400mm × 400mm × 100mm. The bottom of the gas chamber is open and embedded in the gas chamber base, covering the soil surface. The top cubic support platform 1 has a mounting base for connecting to the three-axis robotic arm. Air inlets 23 and outlets 22 are located at 250mm and 50mm from the side walls, respectively, and are connected in series via hoses to an air pump, a mass flow meter, and a gas sensor. Guide plates 21 are installed at the outlets 22 and 23 inside the gas chamber. The openings of the guide plates 21 at the inlets 23 and 22 are 50mm and 250mm from the soil surface, respectively. The guide plates 21 guide the airflow at the inlets and outlets 22, reducing the interference of the concentration at the inlets and outlets 22 on the robotic arm sensors.

[0065] Example 2,

[0066] An in-situ measurement method for soil trace gas emission rates based on a three-axis robotic arm includes:

[0067] S1, Install the air chamber base in the area to be measured, install the cubic support platform 1 and the cylindrical air chamber body 2 on the base and seal them, install the air pump and air flow monitoring sensor on the air outlet 22 and air inlet 23 side of the air chamber respectively, and set the parameters of the two air flow monitoring sensors at the air outlet 22 and air inlet 23 to be consistent.

[0068] S2, Sensors are installed on the three-axis robotic arm, and the control module 11 controls the three-axis robotic arm to move and obtain the rate of change of trace gas concentration at multiple points inside the gas chamber;

[0069] S3. Set 15 measurement points in the cylindrical gas chamber body 2. When the average rate of change of each point in the cylindrical gas chamber body 2 is lower than the set threshold, the system is determined to have reached steady state. When the average rate of change of each point in the gas chamber is higher than the set threshold, a dynamic weighted average algorithm based on spatial weight allocation is adopted. Combined with the flux calculation model under unsteady state, the soil trace gas flux is finally obtained.

[0070] This invention sets 15 measurement points inside the gas chamber, divided into lower, middle, and upper layers, at distances of 50mm, 150mm, and 250mm from the soil surface, respectively. Each layer has 5 measurement points, and the distribution of these points is consistent across all layers. The measurement points are divided into a center point and four vertices. The center point is located on the axis of the two chambers within the cylindrical gas chamber. Excluding the center point, the other four vertices are 100mm away from the center point, forming a square around it. These five measurement points cover most of the area at the same height within the gas chamber. The distribution of the measurement points and the movement trajectory of the robotic arm are as follows: Figure 4 As shown.

[0071] During the measurement, the gas sensor at the end of the robotic arm measures the rate of change of the target trace gas at various points inside the gas chamber. First, the sensor at the end of the robotic arm moves to the center measurement point in the lower layer (50mm from the soil surface) to obtain the rate of change of trace gas concentration (dC) at that point. i After receiving the data ( / dt, i = 1…15), the robotic arm will follow... Figure 4 The robotic arm moves along a trajectory, measuring the remaining points on the same layer. Once data from all measurement points on that layer has been collected, the end effector sensor will move to the middle and upper layers to perform the same operation. After data from all layers has been collected, it returns to its initial position (the center measurement point on the lower layer) for the next round of measurements. The robotic arm's movement speed can be determined by simulating the gas chamber environment using fluid simulation software, ensuring that the robotic arm's movement does not interfere with the airflow mixing or the original gas concentration inside the gas chamber.

[0072] The state inside the gas chamber is determined by averaging the rate of change of target trace gas concentration at 15 measurement points in the synchronous belt. If the average value is less than a pre-set threshold, the gas chamber can be considered to have reached a steady state; otherwise, it has not. Different calculation formulas are used to calculate soil trace gas flux for different gas chamber states.

[0073] When the gas chamber is determined to have reached a steady state, the soil trace gas flux is calculated using the flux calculation formula under steady-state conditions, combined with the gas concentrations obtained from inlet 23 and outlet 22. The calculation formula is as follows:

[0074]

[0075] Where A is the soil area covered by the gas chamber, F represents the flux of the target trace gas inside the gas chamber, Q represents the gas flow rate at the inlet / outlet 22, and C in and C out These represent the concentrations of the target trace gas at inlet 23 and outlet 22, respectively.

[0076] When the gas chamber is determined to be in an unsteady state, the soil trace gas flux is calculated using the dynamic weighted average algorithm proposed in this invention.

[0077] Dynamic weighted average algorithm:

[0078] 1. Single-point flux calculation

[0079] Gas concentration change rate at each measurement point Synchronous belt 15 combined with the target trace gas concentration C at the inlet and outlet in and C out The flux data F at each measurement point is calculated using the flux calculation formula under unsteady state. i The formula for calculating flux under unsteady state is as follows:

[0080]

[0081] In the formula, Let V be the rate of change of trace gas concentration at each measurement point, ignoring the differences in volume distribution inside the gas chamber, meaning that all measurement points share the same volume V, and i represents the measurement point location.

[0082] Spatial weight allocation strategy;

[0083] Table 1 shows the weight allocation for each measurement point:

[0084] Location Weight base β Gradient sensitivity coefficient α Lower layer center point 1.5 0.5 Lower vertex 1.2 0.7 Mid-level center point 1.0 0.4 Mid-level vertices 0.8 0.6 upper center point 0.7 0.5 upper vertex 0.5 0.7

[0085] Because the lower layer is in direct contact with the soil source, the trace gas release rate is closest to the true value, and the data reliability is the highest, so the weight base is the largest; due to the addition of the baffle, the upper and lower layers are significantly affected by the turbulence of the inlet and outlet, resulting in a large gradient noise, so the gradient sensitivity coefficient is large.

[0086] Dynamic weight calculation formula:

[0087]

[0088] In the formula, j represents the number of the 15 measurement points; C represents the trace gas concentration; and e represents the natural constant. The gradient modulus is the value of each measurement point. The gradient modulus characterizes the spatial variation intensity of trace gas concentration around the measurement point, and the calculation formula is as follows:

[0089] For the center point, calculate the root mean square of the radial gradient with respect to the four vertices:

[0090]

[0091] In the cylindrical air chamber body 2, only the gradient between the four vertices of the same horizontal plane and the two adjacent points is calculated.

[0092] The steps described above yield Fi and ω. i The weighted average is calculated using the following formula:

[0093]

[0094] In the formula, F avg This represents the soil trace gas flux when the gas chamber is in a non-steady-state condition.

[0095] Derivation of the flux calculation formula:

[0096] This invention relates to a soil trace gas flux measuring instrument based on an open-type circulating air chamber. Its flux calculation model is based on the law of conservation of mass, which states that in a closed or open system, the mass of a component cannot be created or destroyed; it can only be changed through inflow and outflow at the system boundary, or through generation or consumption within the system. Specifically, the rate of change = inflow - outflow + generation - consumption, expressed as:

[0097] ΔM=M in -M out +M pro -M con

[0098] In the formula, M in M represents the rate of change in inflow; out M represents the rate of change in outflow; pro Indicates the rate of change; M conIndicates the rate of change in consumption;

[0099] When measuring using the gas chamber method, no chemical reaction occurs inside the gas chamber with trace gases, therefore M con Item and M pro With the term set to zero, we obtain the following formula:

[0100] ΔM=M in -M out

[0101] Based on the above law, the gas flux inside an open flow chamber can be expressed by the formula:

[0102]

[0103] Where V represents the volume of the air chamber, and V is a constant, the above formula can be simplified to:

[0104]

[0105] In the formula, V represents the volume of the air chamber. This represents the rate of change of the target gas concentration inside the gas chamber, where A is the soil area covered by the gas chamber, and Q represents the gas flow rate C at the inlet / outlet 22. in and C out The concentrations of the target gas at inlet 23 and outlet 22 are respectively represented, and R represents the rate at which trace gases emitted from the soil enter the gas chamber.

[0106] The formula for the trace gas flux F released per unit area of ​​soil can be expressed as:

[0107]

[0108] Where A represents the area of ​​contact between the bottom of the air chamber and the soil, substituting it into the equation, we get:

[0109]

[0110] The above formulas can be rearranged as follows:

[0111]

[0112] If the gas chamber operates for a sufficiently long time, the system will reach a steady state, i.e.:

[0113]

[0114] This equation simplifies to:

[0115]

[0116] Based on the substitutation, the specific formula for calculating soil trace gas flux in an open dynamic gas chamber is as follows:

[0117]

[0118] The specific implementation methods described above are as follows:

[0119] First, install the gas chamber base in the soil area to be tested, and install the gas chamber on the base. Add water to the groove where the base and the gas chamber fit together to form a seal. Adjust the air pump and mass flow meter at the air inlet 23 and air outlet 22 on the side wall of the gas chamber so that ambient air is drawn into the gas chamber as a compensation gas. Set the parameters of the two mass flow meters to be the same so that the gas flow rate entering and exiting the gas chamber is the same. After the settings are completed, record the target trace gas concentration at the air inlet 23 and air outlet 22 until the measurement is completed.

[0120] Then, turn on the power switch of the robotic arm to start it working. First, the robotic arm will move the target gas sensor to the center measurement point of the gas chamber, 50mm above the soil surface, at the movement speed obtained from fluid simulation. Then, it will proceed according to... Figure 4 The robotic arm moves along its trajectory (its movement speed is always the speed obtained from the fluid simulation). When the sensor reaches each measurement point, it pauses for a period longer than the sensor's sampling time to ensure it can measure changes in the target gas concentration. This process is repeated at distances of 150mm and 250mm from the soil, resulting in data from 15 measurement points. After all points have been collected, the sensor at the end of the robotic arm returns to the center measurement point 50mm from the soil surface for the next round of measurements. The data collected by the sensor is transmitted to a host computer via the control system, where it is processed and further analyzed.

[0121] The concentration change rate collected at 15 measurement points After averaging, we obtain ΔC. ave If ΔC ave If the flux exceeds a pre-set threshold, the gas chamber is considered to be in a non-steady state; otherwise, the gas chamber is considered to be in a steady state. When the gas chamber is in a steady state, the soil trace gas flux can be directly calculated using the flux calculation model; when the gas chamber is in a non-steady state, the soil trace gas flux needs to be calculated using the dynamic weighted average algorithm proposed in this invention.

[0122] This invention uses a three-axis robotic arm equipped with gas sensors to perform path scanning within a gas chamber, acquiring concentration change rate distribution data at different locations within the gas chamber. This improves the accuracy of gas chamber status judgment, effectively eliminates spatial representativeness errors caused by traditional single-point measurements, and more accurately calculates soil trace gas flux. Furthermore, this invention eliminates the need to place multiple gas sensors inside the gas chamber to acquire gas concentration distribution data, significantly reducing sensor costs.

[0123] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0124] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for in-situ measurement of soil trace gas emission rate based on three-axis mechanical arm, comprising a gas chamber, the gas chamber comprises a cubic bearing platform (1) and a cylindrical gas chamber body (2), the cylindrical gas chamber body (2) is installed on the lower surface of the cubic bearing platform (1), the cylindrical gas chamber body (2) and the cubic bearing platform (1) are in communication with each other, characterized in that, The upper surface of the cubic bearing platform (1) is provided with a control module (11), and the cubic bearing platform (1) is provided with a three-axis mechanical arm.

2. The in-situ measurement device for soil trace gas emission rate based on three-axis mechanical arm according to claim 1, characterized in that, The control module (11) is composed of a main controller, a power module and a motor driver, and the main controller controls the three-dimensional movement of the mechanical arm in the cubic bearing platform (1) and the cylindrical air chamber body (2). The power module is responsible for power supply of the whole device.

3. The in-situ measurement device for soil trace gas emission rate based on three-axis mechanical arm according to claim 2, characterized in that, The three-axis mechanical arm includes a slide rail (13), a slide table (14) and a synchronous belt (15), the slide rail (13) includes a first slide rail, a second slide rail, a third slide rail and a fourth slide rail, the slide table (14) is slidably installed on the slide rail (13) at both sides of the bottom end, the bottom of the slide table (14) is fixedly installed on the synchronous belt (15), one end of the slide rail (13) is fixedly provided with a stepping motor (16), the stepping motor (16) is used to drive the synchronous belt (15) to move on the slide rail (13), one end of the synchronous belt (15) is drivingly connected in the middle of the slide rail (13), and the other end of the synchronous belt (15) is drivingly installed on the driving shaft of the stepping motor (16).

4. The in-situ measurement device for soil trace gas emission rate based on three-axis mechanical arm according to claim 3, characterized in that, The first slide rail, the second slide rail, the third slide rail and the fourth slide rail are uniformly provided with the slide table (14) and the synchronous belt (15), the first slide rail and the second slide rail are symmetrically installed at both sides of the bottom of the cubic bearing platform (1), one end of the third slide rail is fixedly installed on the slide table (14) in the first slide rail, the other end of the third slide rail is fixedly installed on the slide table (14) of the second slide rail, the fourth slide rail is fixedly installed on the slide table (14) of the third slide rail, and the slide table (14) fixedly installed on the other end of the fourth slide rail away from the third slide rail is provided with a target gas sensor (24), and the target gas sensor (24) is arranged in the cylindrical air chamber body (2).

5. The apparatus and method according to claim 4, wherein, The inner wall of the cylindrical air chamber body (2) is symmetrically provided with an air inlet (23), the inner wall of the cylindrical air chamber body (2) is respectively provided with an air outlet (22) and the air inlet (23), and the guide plate (21) is installed on the cubic bearing platform (1) close to the air outlet (22) and the air inlet (23).

6. A method for in-situ measurement of soil trace gas emission rate based on a triaxial mechanical arm, suitable for the in-situ measurement device of soil trace gas emission rate based on a triaxial mechanical arm according to any one of claims 1-5, characterized in that, It includes: S1, installing an air chamber base in a measured area, installing the cubic bearing platform (1) and the cylindrical air chamber body (2) above the base and sealing, installing an air pump and an air flow monitoring sensor on one side of the air outlet (22) and the air inlet (23) of the air chamber respectively, and setting the parameters of the air flow monitoring sensors at the air outlet (22) and the air inlet (23) to be consistent; S2, installing a sensor on the three-axis mechanical arm, and controlling the three-axis mechanical arm to move to obtain the trace gas concentration change rate of multiple points in the air chamber through the control module (11). S3, 15 measuring points are arranged in the cylindrical gas chamber body (2), when the average change rate of each point in the cylindrical gas chamber body (2) in the gas chamber is lower than the set threshold, it is determined that the system reaches steady state, when the average change rate of each point in the gas chamber is higher than the set threshold, a dynamic weighted average algorithm based on space weight distribution is adopted, combined with the flux calculation model under non-steady state, and finally the soil trace gas flux is obtained.

7. The method according to claim 6, wherein, When each point in the gas chamber in S3 reaches steady state, the soil trace gas flux is calculated by using the flux calculation formula under steady state combined with the gas concentration obtained from the gas inlet (23) and the gas outlet (22), and the calculation formula is as follows: where A is the soil area covered by the chamber, F represents the flux of the target trace gas inside the chamber, Q represents the gas flow at the inlet (22), C in and C out represent the concentration of the target trace gas at the inlet (23) and at the outlet (22), respectively; The soil trace flux calculation formula under non-steady state in S3 is as follows: wherein is the rate of change of trace gas concentration for each measurement point, ignoring differences in volume distribution within the chamber, i.e. all measurement points share the same volume V, i denotes the measurement point location.

8. The method according to claim 7, wherein, The dynamic weight calculation formula in the dynamic weighted average algorithm in S3 is as follows: In the formula, j represents the number of 15 measuring points; C represents the concentration of trace gas; e represents the natural constant; The gradient modulus of each measuring point is represented by G, which represents the spatial variation intensity of the trace gas concentration around the measuring point, and the calculation formula is as follows: Wherein, the four vertices of the same horizontal plane in the cylindrical gas chamber body (2) only calculate the gradient with the adjacent two points; Obtain Fi and ω in the above step i Weighting is performed, and the specific formula is as follows: where F avg is the soil trace gas flux expressed as the non-steady state condition of the air chamber.

9. The method according to claim 8, wherein, The flux calculation model is based on the law of conservation of mass of components, that is, in a closed or open system, the mass of a certain component cannot be produced or disappeared, it can only change through inflow, outflow or generation or consumption in the system, that is, the change rate = inflow-outflow + generation-consumption, and the formula is as follows: ΔM = M in - M out + M pro - M con In the formula, M in represents inflow rate of change; M out represents outflow rate of change; M pro represents generation rate of change; M con represents consumption rate of change; When the gas cell method is used for measurement, no chemical reaction occurs inside the gas cell with trace gases, then M con term and M pro term are zero, the following formula is obtained: ΔM = M in - M out Based on the above law, the gas flux in the open flow-through gas chamber is expressed by the formula as follows: Wherein, Vtable is the volume of the gas chamber, and the above formula is simplified as follows: where V is the volume of the chamber, represents the rate of change of the target gas concentration within the chamber, A is the area of soil covered by the chamber, Q represents the gas flow rate at the inlet (22) and C in and C out represent the concentration of the target gas at the inlet (23) and outlet (22) respectively, and R represents the rate at which trace gases are emitted from the soil into the chamber; The formula of soil trace gas flux released per unit area F can be expressed as follows: Wherein, A represents the area of the bottom of the gas chamber in contact with the soil, and according to the arrangement, the formula for calculating the soil trace gas flux in the open dynamic gas chamber is as follows:

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