Method and system for realizing same-angle opening and closing of laser tree measurer clamping arm and laser tree measurer

Abstract

This application discloses a method, system, and laser tree measuring instrument for achieving the same angle opening and closing of the clamping arms, belonging to the field of forestry carbon sequestration measurement technology. It involves installing two clamping arm bases through the same hinge shaft collar to form a coplanar horizontal cantilever section; establishing a one-to-one transmission relationship by fixing a pair of involute sector gears with equal pitch circle radii to the inner sides of the roots of the two bases; setting an elastic connector between the bases of the two bases so that the line of action of the tension force passes through the gear meshing point; installing magnets on the two sector gears; and arranging Hall sensors inside the main housing, with the two Hall sensors distributed at a 180-degree central angle relative to the hinge shaft axis; calculating the clamping arm opening angle based on the angle data detected by the Hall sensors. Through synchronous control of gear transmission, geometric coplanar constraints, and dual Hall angle measurement verification, the laser diameter measurement reference offset error is reduced, providing highly reliable angle reference data for accurate carbon sequestration calculation.

Description

Technical Field

[0001] This application relates to the field of forestry carbon sequestration measurement technology, and more specifically, to a method, system, and laser tree measuring instrument for realizing the opening and closing of the clamp arm at the same angle. Background Technology

[0002] In the precise accounting of forestry carbon sequestration, the accuracy of trunk diameter at breast height (DBH) and cross-sectional area directly determines the reliability of carbon storage assessment. Laser tree measuring instruments, due to their high measurement speed and accuracy, have gradually replaced traditional tools and become the mainstream equipment. However, in this specific application scenario, they face technical challenges such as insufficient control accuracy of the clamping arms and easy deviation of the angle measurement reference. Existing laser tree measuring instruments mostly use multi-point scanning or lidar signals, which are complex to operate and difficult to control errors; or they use separately driven clamping arm structures, making it difficult to ensure synchronous opening and closing of the two arms, resulting in inconsistent measurement reference planes and hindering large-scale application in grassroots forestry surveys.

[0003] Specifically, the existing technology has the following drawbacks: First, the opening and closing of the clamping arms lacks mechanically forced synchronous constraints, and the angles of the two arms are prone to differ, leading to a shift in the measurement geometric reference. Second, the angle detection is separated from the transmission mechanism, and the sensor installation position is easily affected by vibration, resulting in poor long-term stability. Third, the elastic clamping force is unevenly distributed, and the normal forces exerted by the two arms on the tree trunk are unequal, affecting the triggering accuracy of laser ranging. Fourth, there is a lack of a real-time verification mechanism for angle measurement, making it impossible to identify systematic errors caused by gear wear, sensor failure, etc.

[0004] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0005] The purpose of this application is to provide a method and control system for the synchronous opening and closing of the clamping arm of a laser tree measuring instrument at the same angle. This method has the advantages of enabling the clamping arm to open and close synchronously without slippage or backlash, improving the accuracy of angle measurement and the reliability of data, and providing highly reliable angle reference data for accurate carbon sequestration accounting.

[0006] In a first aspect, this application provides a method for achieving the same-angle opening and closing of the clamping arm of a laser tree measuring instrument, including: The base shanks of the two clamping arms are installed through the same hinge collar, so that the two base shanks extend from the collar and are bent to form a horizontal cantilever section in the same plane. A pair of involute sector gears with equal pitch circle radii are fixed to the inner side of the root of the horizontal cantilever section of the two base shanks, so that the two gears mesh with each other to establish a one-to-one transmission relationship between the change of the clamping arm angle and the rotation of the gears. An elastic connector is provided between the bases of the two base shanks, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears. Magnets are set on the two sector gears respectively, and Hall sensors are arranged in the main housing at the corresponding positions of the magnets, so that the two Hall sensors are distributed at a central angle of 180 degrees relative to the hinge axis. The opening angle of the clamping arm is calculated based on the angle data detected by the Hall sensor.

[0007] Furthermore, an elastic connector is provided between the bases of the two base shanks, such that the line of action of the tension of the elastic connector passes through the meshing point of the two gears, including: Adjust the position of the connection point of the elastic connector on the two base shanks so that the line of action of the tension of the elastic connector coincides with the common tangent of the meshing point of the two gears; When the two clamping arms are in the closed state, the tension of the elastic connector is transmitted through the gear meshing point, causing the two gears to generate a preload force that meshes with each other; When the operator pulls open the clamping arms, the meshing force at the gear meshing point and the tension of the elastic connector form a dynamic force balance, causing the two clamping arms to open synchronously. Once the clamping arms are in contact with the tree trunk, the tension of the elastic connector is transmitted through gear meshing to the normal clamping force of the two clamping arms on the tree trunk, and the clamping forces of the two clamping arms are equal in magnitude.

[0008] Furthermore, based on the angle data detected by the Hall sensor, the opening angle of the clamping arm is calculated, including: When the clamping arm is in the closed state, the output values ​​of the two Hall sensors are collected as the zero-point reference value; During the opening and closing of the clamping arm, the current output values ​​of the two Hall sensors are collected in real time, and the difference between the current output value and the zero-point reference value is calculated to obtain the rotation angle of the two gears. Calculate the arithmetic mean of the two rotation angles to obtain the average rotation angle of the gear; The actual opening angle of the clamp arm is obtained by adding the average rotation angle of the gear to the preset initial opening angle of the single arm.

[0009] Furthermore, the step of acquiring the output values ​​of two Hall sensors as zero-point reference values ​​when the clamping arm is in the closed state includes: During the device startup and initialization phase, the output values ​​of the two Hall sensors are collected in real time, and the rate of change of the output values ​​at adjacent sampling times is calculated. When the rate of change of the output values ​​of both Hall sensors is less than a preset threshold and the difference between the two output values ​​is less than a preset synchronization threshold, the clamp is determined to be in a stable closed state. The output values ​​of the two Hall sensors at this time are used as the zero-point reference values ​​respectively.

[0010] Furthermore, after calculating the arithmetic mean of the two rotation angles to obtain the average rotation angle of the gear, the process further includes: Calculate the difference between the two rotation angles; when the difference exceeds the preset threshold, it is determined to be an abnormal gear meshing or Hall sensor failure, and an abnormal prompt message is output. When the difference is within the preset threshold range, half of the difference is superimposed on the two rotation angles respectively, and symmetrical correction is performed to obtain the corrected rotation angle, so as to eliminate the error caused by the eccentric installation of the magnet or the radial runout of the gear. The corrected rotation angle is added to the initial opening angle of the single arm to obtain the actual opening angle of the clamping arm.

[0011] Furthermore, the step of mounting the base shanks of the two clamping arms through the same hinge collar, so that the two base shanks extend from the collar and are bent to form a horizontal cantilever section on the same plane, includes: The two base shanks are designed with different intermediate fold line lengths so that the two base shanks extend out in the same horizontal plane after being bent. The angle bisector arm is configured as a sliding structure, allowing it to pass through an independent channel on the main housing and through the center of the hinge axis of the two clamping arms, with the bottom surface of the channel being higher than the plane containing the two clamping arms. A bending structure is set at the front end of the angle bisector arm so that the front contact of the angle bisector arm is pressed down and is in the same measuring plane as the front contact of the two clamping arms.

[0012] Furthermore, the step of setting magnets on the two sector gears respectively; and the step of arranging Hall sensors in the main housing at positions corresponding to the magnets, includes: A blind hole is made on the back of the non-meshing side teeth of each sector gear, and a magnet is embedded in the blind hole for fixation; insulating tape is then covered on the surface of the magnet. A plastic pillar is set inside the main housing, a sensor board is installed on the plastic pillar, and the Hall sensor is set on the sensor board. Adjust the position of the sensor board to create a gap between the Hall sensor and the magnet; the Hall sensor is connected to the host via a wire and transmits the detected electrical signal to the host.

[0013] Furthermore, the provision of an elastic connector between the bases of the two base handles further includes: Based on the diameter range of the tree trunk to be tested, select elastic connectors with different elastic coefficients; The preload of the elastic connector is adjusted to an initial value that is compatible with the trunk diameter range, so that the clamping arm generates a normal clamping force when it is attached to the trunk, and the magnitude of the clamping force is positively correlated with the trunk diameter.

[0014] Secondly, this application also proposes a laser tree measuring instrument clamp arm opening and closing control system at the same angle, comprising: The base shank mounting module installs the base shanks of the two clamping arms through the same hinged collar, so that the two base shanks extend from the collar and are bent to form a horizontal cantilever section on the same plane. The gear transmission module has a pair of involute sector gears with equal pitch circle radii fixed on the inner side of the root of the horizontal cantilever section of the two base shanks, so that the two gears mesh with each other to establish a one-to-one transmission relationship between the change of the clamping arm angle and the rotation of the gears. The elastic connection module has an elastic connector between the bases of the two bases, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears. The angle detection module has magnets on two sector gears and Hall sensors arranged in the main housing at positions corresponding to the magnets, so that the two Hall sensors are distributed at a 180-degree central angle relative to the hinge axis. The angle calculation module calculates the opening angle of the clamping arm based on the angle data detected by the Hall sensor.

[0015] Thirdly, this application also proposes a laser tree measuring instrument, including a laser tree measuring instrument clamp arm opening and closing control system as described in the second aspect; Two clamping arms, each clamping arm comprising a base shank and a horizontal cantilever section; The main unit housing is used to house the angle detection module and the angle calculation module; The base shank is mounted to the main housing via the same hinged collar, and the horizontal cantilever section extends from the collar and is bent, with the two horizontal cantilever sections side by side on the same horizontal plane.

[0016] As can be seen from the above, the laser tree measuring instrument clamp arm opening and closing method and control system provided in this application achieves the same angle opening and closing of the clamp arm by means of the same hinged shaft sleeve to achieve coplanar constraint of the base shank, establishes a one-to-one transmission relationship by the involute sector gears with equal pitch circle radii, achieves symmetrical force decomposition by the line of action of the elastic connecting piece tension through the gear meshing point, and achieves angle detection and error correction by the 180-degree central angle distribution of two Hall sensors. It solves the technical problems of asynchronous opening and closing of the laser tree measuring instrument clamp arm, offset of angle measurement reference, and asymmetric clamping force. It has the advantages of being able to achieve synchronous opening and closing of the clamp arm without slippage or backlash, improving the accuracy of angle measurement and data reliability, and providing highly reliable reference data for accurate carbon sequestration accounting. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the steps of the laser tree measuring instrument clamp arm opening and closing at the same angle as disclosed in the embodiments of the present invention; Figure 2 This is a schematic diagram of the three-arm coplanar measurement structure of the laser tree measuring instrument disclosed in the embodiments of the present invention; Figure 3 This is a schematic diagram of the steps disclosed in an embodiment of the present invention, in which an elastic connector is provided between the bases of two base shanks, and the line of action of the tension of the elastic connector passes through the meshing point of the two gears. Figure 4 This is a schematic diagram of the control system for the same angle opening and closing of the clamping arm of the laser tree measuring instrument disclosed in an embodiment of the present invention. Detailed Implementation

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these embodiments belong; the terminology used herein and in the specification of the application is for the purpose of describing particular embodiments only and is not intended to limit these embodiments; the terms "comprising" and "having," and any variations thereof, in the specification of these embodiments and the foregoing drawings, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification of these embodiments and the foregoing drawings are used to distinguish different objects, not to describe a particular order.

[0020] The implementation details of the technical solution in this embodiment are described in detail below: This application proposes a method for achieving the same-angle opening and closing of the clamping arm of a laser tree measuring instrument, such as... Figure 1 As shown, the method includes: S101, the base shanks of the two clamping arms are installed through the same hinged collar, so that the two base shanks extend from the collar and are bent to form a horizontal cantilever section in the same plane.

[0021] like Figure 2The diagram shows the three-arm coplanar measurement structure of the laser tree measuring instrument in this embodiment. The main unit B serves as the measurement reference center, integrating a laser emitter. It forms a three-arm measurement system through openable clamping arms and an angle bisector arm. The two openable clamping arms are symmetrically arranged; their bases are positioned by a collar, then raised at an angle before extending horizontally to form a circular clamping arm body. A pair of involute sector gears are fixed at the angles of the two arms to achieve meshing transmission at the same angle, ensuring a 1:1 relationship between the change in the angle of the two clamping arms and the rotation of the gears during opening and closing. The angle bisector arm, in a flat strip structure, passes independently through the main unit. Its front end, after being pressed down at an angle, merges with the front end of the clamping arm at the "three-arm front end." The contact point of the three-arm front end and the contact point A on the tree trunk surface form the measurement reference plane. The laser beam emitted by the laser emitter points along the direction of the angle bisector arm towards the measuring point P on the tree trunk surface. d is the measured distance from the front end of the angle bisector arm to the tree trunk surface, and r is the tree trunk radius. , These are the effective arm lengths of the two clamping arms (the straight-line distance from point B to point A). Due to the symmetrical constraint of gear transmission with the same diameter, , With the angles always equal and the initial single-arm opening angle θ0 = 5° (the initial angle of the closed state caused by structural interference), the trunk diameter at breast height can be calculated from d and the total opening angle θ based on the Pythagorean theorem of tangent to the circle. The illustrated structure achieves real-time cross-verification of angle data and opening and closing of the clamping arms at the same angle through gear-dual Hall effect coordinated control, providing a highly reliable geometric benchmark for accurate carbon sequestration calculation.

[0022] Specifically, the base of the two clamping arms is fitted onto the same hinge collar, which has an inner diameter of 6mm, an outer diameter of 8mm, and a length of 12mm, serving as the common rotation fulcrum for the two bases. The two bases are integrally machined from 7075 aluminum alloy. Extending outwards from the collar, they undergo two bends to form horizontal cantilever sections. On the left base, the first bend point is 7.5mm from the center of the collar, with a 45° angle. After the first bend, the vertical extension length is 12mm. The second bend point is 14mm from the first bend point, with a 45° angle, forming the horizontal cantilever section. On the right base, the first bend point is 9.5mm from the center of the collar, with a 45° angle. After the first bend, the vertical extension length is 10mm. The second bend point is 16mm from the first bend point, with a 45° angle, forming the horizontal cantilever section. By designing the two base handles with different intermediate bend lengths (14mm on the left and 16mm on the right), the horizontal cantilever sections of the two base handles are precisely in the same horizontal plane after two bends. Measurements using a coordinate measuring machine showed that the vertical distance between this plane and the plane containing the hinge axis is 3.2mm, and the height difference between the two horizontal cantilever sections is less than 0.05mm. This coplanar constraint ensures that the two clamping arms always move within the same plane during subsequent opening and closing, avoiding measurement reference offset caused by torsional deformation. When the clamping arms are opened to their maximum angle of 45°, the vertical projection deviation of the contact points at the front ends of the two clamping arms is still less than 0.1mm.

[0023] S102, a pair of involute sector gears with equal pitch circle radii are fixed on the inner side of the root of the horizontal cantilever section of the two base shanks, so that the two gears mesh with each other to establish a one-to-one transmission relationship between the change of the clamping arm angle and the rotation of the gears.

[0024] Specifically, a planar mounting surface is machined on the inner root of each of the two horizontal cantilever sections of the base shank, and an involute-toothed sector gear is fixed using M2 screws. Both gears have a module of 0.3mm, 20 teeth, and a pitch circle radius r = 0.3 × 20 / 2 = 3mm. The gear material is wear-resistant brass, and the tooth surfaces are precision milled to a tooth profile error of less than 0.01mm. During installation, the relative positions of the two base shanks are adjusted so that the pitch circles of the two gears are tangent, with a center distance of 6mm. When the two clamping arms rotate around the center of the collar, the two gears remain tightly meshed. According to the gear transmission principle, the pitch circle linear velocities of two meshing gears are equal, i.e., v = ω1 × r1 = ω2 × r2. Since r1 = r2 = 3mm, ω1 = ω2, meaning the angular velocities of the two gears are equal. Furthermore, because the gears are fixed to the base shanks, the rotation angle of the gears is the same as the rotation angle of the clamping arms around the center of the collar, therefore θ1 = θ2. Let the opening angle of the clamping arms be α, then the rotation angle of a single clamping arm is α / 2 (considering symmetry), and the gear rotation angle is θ = α / 2. When the clamping arms open from the initial closed state (single arm opening angle 5°) to a single arm opening angle of 45°, a single clamping arm rotates 40°, and the gear rotates accordingly by 40°, strictly satisfying the one-to-one transmission relationship. This design ensures that regardless of whether the operator pulls with one hand or both hands, the two clamping arms always open and close synchronously at the same angle. Test measurements show that within the opening range of 0° to 45°, the difference in the opening angle between the two clamping arms is always less than 0.05°.

[0025] S103, an elastic connector is provided between the bases of the two base shanks, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears.

[0026] Specifically, a spring lug is installed at the root of each of the two base handles near the hinge collar. The lug on the left base handle is located 8mm from the center of the collar on the inner side of the base handle, and the lug on the right base handle is also located 8mm from the center of the collar on the inner side of the base handle. A tension spring is installed between the two lugs. The spring has a free length of 10mm, a wire diameter of 0.5mm, a pitch diameter of 4mm, and an elastic modulus k = 0.6N / mm. The circumferential installation angle of the lugs on the base handles is adjusted so that the axial direction of the spring is aligned with the direction of the common tangent at the meshing point of the two gears. The angle θ between the common tangent at the meshing point of the two gears and the horizontal direction is calculated. tan=arctan(base shank bending height / base shank horizontal projection length) =arctan(3.2 / 25) = 7.3°. By rotating the mounting angle of the lug, the angle between the spring axis and the horizontal direction is also 7.3°. At this time, the line of action of the spring tension passes precisely through the meshing point of the two gears. When the two clamping arms are in the closed state, the angle between the two base shanks is 10°, the spring is stretched to 12mm, the elongation ΔL = 2mm, and the spring tension Fspring = k × ΔL = 0.6 × 2 = 1.2N. This tension is transmitted through the gear meshing point, so that the teeth of the two gears generate a preload of 1.2N at the meshing point, completely eliminating the inherent tooth backlash in the gear transmission. When the clamping arms are opened to a single arm angle of 25° (i.e., the angle between the two base shanks is 60°), the spring is stretched to 16.5mm, the elongation ΔL = 6.5mm, and the spring tension Fspring = 0.6 × 6.5 = 3.9N. The tension is transmitted through the gear meshing point, so that the two clamping arms produce equal normal clamping forces on the tree trunk. The clamping force is calculated to be Fnormal = Fspring × L1 / L2 = 3.9 × 25 / 150 = 0.65 N, where L1 is the distance from the spring action point to the center of the collar (25 mm) and L2 is the length of the clamping arm (150 mm).

[0027] This embodiment further proposes a method for setting the above-mentioned elastic connector, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears. For example... Figure 3 As shown, an elastic connector is provided between the bases of the two base shanks, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears, specifically including: S3001, Adjust the position of the connection point of the elastic connector on the two base shanks so that the line of action of the tension of the elastic connector coincides with the common tangent of the meshing point of the two gears; S3002, when the two clamping arms are in the closed state, the tension of the elastic connector is transmitted through the gear meshing point, causing the two gears to generate a preload force for meshing with each other; S3003: When the operator pulls open the clamping arms, the meshing force at the gear meshing point and the tension of the elastic connector form a dynamic force balance, causing the two clamping arms to open synchronously. S3004, when the clamping arms are attached to the tree trunk, the tension of the elastic connector is transmitted through gear meshing to the normal clamping force of the two clamping arms on the tree trunk, and the clamping forces of the two clamping arms are equal in magnitude.

[0028] Specifically, in this embodiment, a spring lug is installed at the root of each of the two base handles near the hinge collar. The lug on the left base handle is located 8mm from the center of the collar on the inner side of the base handle, and the lug on the right base handle is also located 8mm from the center of the collar on the inner side of the base handle. A tension spring with a free length of 10mm and an elastic modulus of 0.6N / mm is installed between the two lugs. The circumferential installation angle of the lugs on the base handles is adjusted so that the axial direction of the spring is exactly aligned with the common tangent direction of the two gear meshing points. Measurements show that the angle between the common tangent of the two gear meshing points and the horizontal direction is 7.3°. By rotating the installation angle of the lugs, the angle between the spring axis and the horizontal direction is also 7.3°. At this point, the line of action of the spring tension precisely passes through the meshing point of the two gears, ensuring that the spring tension at the gear meshing point generates a pure tangential force and does not produce an additional radial component force that interferes with the normal meshing of the gears.

[0029] When the two clamping arms are initially closed, the angle between the two base handles is 10°. At this time, the spring is stretched to 12mm, with an elongation of 2mm. Based on the spring constant of 0.6N / mm, the tension generated by the spring is Fspring = 0.6 × 2 = 1.2N. Since the line of action of the spring tension passes through the meshing point of the two gears, the tension is decomposed into two equal and opposite forces at the meshing point, acting on the teeth of the two gears respectively. These two forces keep the teeth of the two gears in close contact at the meshing point, generating a preload of approximately 1.2N. This preload completely eliminates the inherent tooth backlash in the gear transmission, allowing the gears to transmit motion immediately when the clamping arms begin to open, without any free travel or return error. Actual measurements show that without the elastic connector, the gear transmission has approximately 0.15° of free travel; with the elastic connector, the free travel is completely eliminated.

[0030] When the operator pulls the support arms apart using the handles, let the total pulling force applied by the operator be Fhand. This pulling force causes the two base handles to rotate outward around the center of the collar, generating a meshing force Fmesh at the gear meshing point in the opposite direction of rotation. Simultaneously, as the opening angle of the clamping arms increases, the angle between the two base handles increases, further stretching the spring, and the spring force Fspring also increases accordingly. At any opening angle, the meshing force Fmesh at the gear meshing point is always equal to the tangential component of the spring force Fspring at that point, forming a dynamic force balance. For example, when the clamping arms are opened to a single arm angle of 15° (i.e., an angle of 40° between the two base handles), the spring is stretched to 15mm, with an elongation of 5mm, and the spring force Fspring = 0.6 × 5 = 3.0N. At this time, the angle between the spring axis and the common tangent of the gear meshing point is 0° (because it has been adjusted to coincide), therefore the meshing force Fmesh = Fspring = 3.0N at the gear meshing point. This balance ensures that regardless of the force applied by the operator, the two gears remain tightly meshed under the constraint of the spring preload, thus ensuring that the two clamping arms open strictly and synchronously. Tests have shown that within the opening range of 0° to 45°, the difference in the opening angle between the two clamping arms is consistently less than 0.05°.

[0031] Once the clamping arms stop rotating and are in contact with the tree trunk, the operator releases the handles. At this point, the spring tension becomes the only force maintaining contact between the clamping arms and the trunk. In a certain measurement, the trunk diameter is 20cm, and the angle between the clamping arms when open is 25° (i.e., the angle between the two base handles is 60°). The spring is stretched to 16.5mm, with an elongation of 6.5mm, and the spring tension Fspring = 0.6 × 6.5 = 3.9N. This tension is transmitted to the two clamping arms through the gear meshing point, generating a rotational torque around the center of the collar on each arm. This torque causes the front end of the clamping arm to exert a normal pressure on the trunk. Through mechanical calculations, the clamping arm length (from the center of the collar to the trunk contact point) is 150mm, and the distance from the spring tension point to the center of the collar is 25mm. Therefore, the torque generated by the spring tension is M = Fspring × 25 = 97.5 N·mm. The normal force generated by this torque at the front end of the clamping arm is Fnormal = M / 150 = 0.65N. Because the two clamping arms have identical geometric dimensions, and the gear meshing forces them to rotate synchronously, the normal clamping force of both arms on the tree trunk is equal in magnitude, both being 0.65N. This equal force ensures that the tree trunk is in a centrally symmetrical position within the clamping arms, providing a stable centering reference for subsequent laser ranging. Actual measurements show that under this clamping force, the clamping arms fit tightly against the tree trunk without damaging the bark.

[0032] This embodiment achieves precise alignment of the line of action of the elastic connector's tension with the common tangent of the gear meshing point through the above four steps. This allows the spring preload to effectively eliminate gear backlash and maintain dynamic force balance during opening and closing, ultimately transforming into equal normal clamping forces on the tree trunk from the two clamping arms. This complete mechanical transmission chain provides a reliable mechanical foundation for the high-precision angle measurement of the laser tree measuring instrument.

[0033] S104, magnets are set on the two sector gears respectively, and Hall sensors are arranged in the main housing at the corresponding positions of the magnets, so that the two Hall sensors are distributed at a 180-degree central angle with respect to the hinge axis.

[0034] Specifically, a blind hole with a diameter of 2.5 mm and a depth of 1.8 mm is drilled on the back of the non-meshing side teeth of each sector gear. A neodymium iron boron magnet (grade N52) with dimensions of 2.5 mm × 2.5 mm × 1.5 mm is embedded in the blind hole and fixed with epoxy resin. The N pole of the magnet faces outward of the gear, and the S pole faces inward of the gear. A layer of polyimide insulating tape with a thickness of 0.05 mm is covered on the surface of the magnet to prevent the magnet from contacting external conductors. On the inside of the main housing, corresponding to the rotation trajectory positions of the two magnets, two plastic posts are set, with a height of 10 mm and a diameter of 6 mm. A sensor board is installed on each plastic post, and a linear Hall sensor (model SS495A, sensitivity 3.125 mV / Gs) is soldered to the sensor board. The position of the sensor board is adjusted so that the gap between the sensitive surface of the Hall sensor and the surface of the magnet is 0.3 mm ± 0.05 mm. Two Hall effect sensors are positioned at a 180-degree central angle relative to the hinge axis. That is, when the clamping arm is in its initial closed position, the two magnets are located on the left and right sides, respectively, with an angle of 180° to the line connecting them to the center of the hinge axis. The two Hall effect sensors are also correspondingly arranged on the left and right sides, with an angle of 180° to the line connecting them to the center of the hinge axis. The Hall effect sensors are connected to the circuit board inside the main unit via three enameled wires (power line VCC=5V, ground line GND, signal line OUT), transmitting the detected analog voltage signal, proportional to the magnetic field strength, to the main unit. Actual measurements show that when the magnets are directly opposite the Hall effect sensors, the output voltage is 3.75V; when the magnets deviate from the center with the gear rotation, the output voltage changes approximately linearly with the rotation angle, with a linearity better than 0.5% within a range of ±45°.

[0035] S105 calculates the opening angle of the clamping arm based on the angle data detected by the Hall sensor.

[0036] It should be noted that in S105, the opening angle of the clamping arm is calculated based on the angle data detected by the Hall sensor, specifically including the following steps: when the clamping arm is in the closed state, the output values ​​of the two Hall sensors are collected as the zero-point reference value; during the opening and closing process of the clamping arm, the current output values ​​of the two Hall sensors are collected in real time, and the difference between the current output value and the zero-point reference value is calculated to obtain the rotation angle of the two gears; the arithmetic mean of the two rotation angles is calculated to obtain the average rotation angle of the gears; the average rotation angle of the gears is added to the preset initial opening angle of the single arm to obtain the actual opening angle of the clamping arm.

[0037] Specifically, in this embodiment, the microcontroller inside the host (e.g., an STM32F103 series) acquires the analog voltage signals output by the two Hall sensors in real time at a sampling frequency of 200Hz, and converts them into digital quantities through a built-in 12-bit analog-to-digital converter with a conversion accuracy of 5V / 4096≈0.00122V. First, zero-point calibration is performed: when the device is powered on and the clamping arm is in a closed and stable state, data from 100 sampling points are continuously acquired, and the arithmetic mean of the output values ​​of the two Hall sensors is calculated as the zero-point reference value. Suppose that in a certain calibration, H10=1.523V and H20=1.477V, the difference between the two is 0.046V, which is less than the preset synchronization threshold of 0.05V, indicating that the clamping arm is in a good closed state. During the opening and closing process of the clamping arm, the current output values ​​H1 and H2 of the two Hall sensors are acquired in real time, and the differences between the current values ​​and the zero-point reference value are calculated as ΔH1=H1-H10 and ΔH2=H2-H20, respectively. Based on the calibration curve of the Hall sensor, the relationship between the voltage change and the gear rotation angle was obtained through experimental calibration: every 1° rotation angle corresponds to a voltage change of 0.035V, i.e., the sensitivity S = 0.035V / °. Therefore, the gear rotation angles θ1 = ΔH1 / S and θ2 = ΔH2 / S.

[0038] For example, if in a certain measurement H1 = 1.873V and H2 = 1.827V, then: ΔH1 = 1.873 - 1.523 = 0.350V ΔH2 = 1.827 - 1.477 = 0.350V θ1 = 0.350 / 0.035 = 10.00° θ² = 0.350 / 0.035 = 10.00° The arithmetic mean of the two rotation angles is calculated as θavg = (θ1 + θ2) / 2 = 10.00°. The initial opening angle of the single arm of this tree measuring instrument is determined to be θ0 = 5° by mechanical design. Adding the average rotation angle of the gear θavg to the initial opening angle of the single arm θ0, we obtain the actual opening angle of the clamping arm α = θavg + θ0 = 10.00° + 5° = 15.00°.

[0039] Furthermore, the step of collecting the output values ​​of the two Hall sensors as zero-point reference values ​​when the clamping arm is in the closed state includes: during the device power-on initialization phase, collecting the output values ​​of the two Hall sensors in real time and calculating the rate of change of the output values ​​at adjacent sampling times; when the rate of change of the output values ​​of the two Hall sensors is less than a preset threshold and the difference between the two output values ​​is less than a preset synchronization threshold, it is determined that the clamping arm is in a stable closed state; and the output values ​​of the two Hall sensors at this time are respectively used as zero-point reference values.

[0040] Specifically, in this embodiment, the device startup initialization phase refers to an automatic execution period after each power-on of the laser tree measuring instrument and before the formal measurement. At this time, the operator has not yet operated the clamping arm, which is theoretically in a naturally closed state. However, due to factors such as transportation vibration, temperature changes, or spring fatigue after long-term use, the actual closed position of the clamping arm may have slight deviations. Therefore, a fixed factory value cannot be simply used as the zero-point reference; instead, it needs to be dynamically determined by monitoring the output of the Hall sensor in real time.

[0041] Real-time acquisition of the output values ​​of two Hall sensors refers to the microcontroller continuously reading the digital values ​​converted from analog to digital by the two Hall sensors at a sampling frequency of 200Hz, denoted as H1[i] and H2[i], where i is the sampling sequence number. Calculating the rate of change of the output values ​​between adjacent sampling times refers to the ratio of the absolute value of the difference between two consecutive samples for each sensor to the sampling time interval, i.e., the rate of change R1[i] = |H1[i] - H1[i-1]| / Δt, R2[i] = |H2[i] - H2[i-1]| / Δt. The sampling time interval Δt = 5ms (corresponding to 200Hz), therefore the unit of the rate of change is V / ms.

[0042] A preset threshold Rth is used to determine whether the clamping arm is in a stationary state. Since the clamping arm may experience minor vibrations (such as shaking when holding the device) in its naturally closed state, the Hall output will fluctuate slightly, but the amplitude of these fluctuations is usually very small. According to extensive experimental statistics, when the clamping arm is completely stationary, the voltage change rate between adjacent sampling points is generally less than 0.002V / ms; when there is a human disturbance, the change rate increases rapidly. In this embodiment, Rth = 0.005V / ms is used as the judgment threshold, meaning that the clamping arm is considered to have entered a stable stationary state only when the change rate of both sensors is less than 0.005V / ms for multiple consecutive tests (e.g., 5 consecutive tests).

[0043] The synchronization threshold ΔHth is used to determine whether the two Hall sensors indicate the same closed position in a steady state. Since there may be slight deviations in the installation of the two magnets, the output values ​​of the two sensors may differ slightly even when the clamping arm is fully closed. However, as long as this difference is within a reasonable range, the clamping arm is considered to be in a normally closed state. In this embodiment, ΔHth = 0.05V is taken, that is, when |H1-H2| < 0.05V, the closed positions indicated by the two sensors are considered to be consistent.

[0044] The condition for determining that the clamp arm is in a stable closed state is that the rate of change of the output values ​​of both Hall sensors is less than Rth, and the difference between the two output values ​​is less than ΔHth. To eliminate random fluctuations, it is usually required that this condition be met continuously a certain number of times (e.g., 10 consecutive samples, i.e., for 50ms) before stability is finally determined.

[0045] The process is illustrated below using a set of actual sampling data. During the device's power-on initialization phase, the microcontroller continuously samples the output voltages of two Hall sensors at a sampling frequency of 200Hz. In a specific test, the data collected from 10 consecutive sampling points (each at a 5ms interval) is as follows: The first sampling point has H1 at 1.523V and H2 at 1.477V; the second sampling point has H1 at 1.524V and H2 at 1.478V, with H1 and H2 changing by 0.001V and 0.001V respectively compared to the previous time point, both at a rate of 0.0002V / ms; the third sampling point has H1 at 1.522V and H2 at 1.476V, both changing by 0.002V, at a rate of 0.0004V / ms; the fourth sampling point has H1 at 1.525V and H2 at 1.479V, with a rate of 0.0006V / ms; the fifth sampling point has H1 at 1.523V and H2 at 1.477V. V, rate of change 0.0004V / ms; 6th sampling point H1 is 1.526V, H2 is 1.480V, rate of change 0.0006V / ms; 7th sampling point H1 is 1.522V, H2 is 1.476V, rate of change 0.0008V / ms; 8th sampling point H1 is 1.524V, H2 is 1.478V, rate of change 0.0004V / ms; 9th sampling point H1 is 1.523V, H2 is 1.477V, rate of change 0.0002V / ms; 10th sampling point H1 is 1.525V, H2 is 1.479V, rate of change 0.0004V / ms.

[0046] Observing the data above, from the 2nd to the 10th sampling point, the rate of change of the output values ​​of the two Hall sensors is between 0.0002V / ms and 0.0008V / ms, which is much smaller than the preset rate of change threshold of 0.005V / ms. Simultaneously, the difference between the output values ​​of the two sensors, |H1-H2|, remains stable at 0.046V at each sampling moment, which is less than the preset synchronization threshold of 0.05V. Since the conditions of rate of change being less than the threshold and difference being less than the synchronization threshold are met for 9 consecutive samplings (from the 2nd to the 10th), it is equivalent to being in a stable state for 45ms, achieving the system's set requirement of 10 consecutive (50ms) stable determinations. Therefore, the microcontroller determines that the clamping arm is in a stable closed state and stores the values ​​H1=1.525V and H2=1.479V at the 10th sampling point as the zero-point reference values ​​H10 and H20 of the two Hall sensors, respectively, for angle calculation during subsequent measurements.

[0047] If an excessive rate of change or an out-of-limit difference is detected during initialization, the system will wait and continuously monitor until the stability condition is met. If the condition cannot be met for an extended period (e.g., more than 5 seconds), the operator will be prompted to check if the gripper arm is stuck or if the sensor is faulty, and it will be recommended to manually close the gripper arm and re-initialize.

[0048] This embodiment automatically identifies whether the clamping arm is truly in a stable closed state by dynamically monitoring the rate of change and difference of the Hall sensor output value, avoiding incorrect zero-point calibration caused by human error or environmental vibration. Simultaneously, using the sensor output value at the moment the stable condition is met as the zero-point reference effectively eliminates zero-point offset caused by device aging, temperature drift, or mechanical wear, laying a reliable foundation for subsequent high-precision angle measurements.

[0049] Furthermore, after calculating the arithmetic mean of the two rotation angles to obtain the average rotation angle of the gear, the method further includes: calculating the difference between the two rotation angles; when the difference exceeds a preset threshold, it is determined to be an abnormal gear meshing or a Hall sensor malfunction, and an abnormal prompt message is output; when the difference is within the preset threshold range, half of the difference is superimposed on the two rotation angles respectively to perform symmetrical correction to obtain the corrected rotation angle, so as to eliminate the error caused by the eccentric installation of the magnet or the radial runout of the gear; the corrected rotation angle is added to the initial opening angle of the single arm to obtain the actual opening angle of the clamping arm.

[0050] Specifically, in this embodiment, during the actual use of the laser tree measuring instrument, slight radial eccentricity may exist at the installation position of the magnet, or a small amount of radial runout may occur when the sector gear rotates. This can cause the gear rotation angles measured by the two Hall sensors to show deviations in opposite directions but similar in magnitude. This deviation manifests as one sensor reading being too high and the other too low, but the average of the two is still close to the true value. While simply using an arithmetic mean can partially offset the error, symmetrical correction can more accurately eliminate this common-mode error, and the magnitude of the difference can also be used for fault diagnosis.

[0051] It should be noted that the preset threshold Δθth is determined based on machining accuracy and experimental statistical results. In this embodiment, based on the machining tolerance of the sector gear (radial runout of the gear ring ≤ 0.02 mm) and the allowable range of magnet installation eccentricity (≤ 0.1 mm), the difference threshold is set to Δθth = 0.2° through theoretical calculations and statistical analysis of numerous prototype tests. When the difference between the two rotation angles exceeds 0.2°, it indicates a possible abnormal gear meshing (such as foreign object jamming), magnet detachment, or Hall sensor malfunction; when the difference is within 0.2°, it is considered to be within the normal range of installation eccentricity or gear runout, and a more accurate angle value can be obtained through correction.

[0052] The implementation process of this method is illustrated below using two sets of measured data.

[0053] First set of data: In a normal measurement scenario, the two rotation angles are basically the same.

[0054] In a certain measurement, the rotation angles of the two gears were calculated based on the Hall sensor output voltage as θ1 = 10.02° and θ2 = 9.98°. The difference Δθ = |10.02 - 9.98| = 0.04°, which is less than the preset threshold of 0.2°. Therefore, half of the difference, 0.02°, was added to both angles for symmetrical correction: θ1' = 10.02 - 0.02 = 10.00°, θ2' = 9.98 + 0.02 = 10.00°. The corrected average rotation angle of the gears remained 10.00° (consistent with the direct averaging result). Adding this corrected rotation angle of 10.00° to the initial opening angle of 5° for the single arm yielded an actual opening angle of 15.00° for the clamp arm. In this example, the results before and after correction are the same, indicating that the readings of the two sensors were already very symmetrical, and the correction operation did not introduce additional error.

[0055] The second set of data shows a scenario with obvious installation eccentricity, where the two rotation angles deviate significantly but are still within the threshold.

[0056] During a measurement, θ1 = 10.15° and θ2 = 9.85° were measured. The difference Δθ = 0.30° exceeded the 0.2° threshold. At this point, the system determined that there might be an anomaly, outputting the message "Please check the gear meshing status or Hall sensor," and paused the measurement process, awaiting operator inspection. Inspection revealed that the magnet's fixing adhesive had slightly loosened due to transportation vibration, causing the magnet's position to shift. After re-fixing, the magnet returned to normal.

[0057] The third set of data shows a slight eccentricity, but it does not exceed the threshold, and the correction effect is obvious.

[0058] After long-term use, a slight eccentricity appeared in the magnet installation of another prototype. A set of data was measured: θ1 = 10.10°, θ2 = 9.90°. The difference Δθ = 0.20°, exactly equal to the threshold. According to the preset rule, values ​​equal to the threshold are still considered within the normal range (correction can be set to apply when the value is ≤ the threshold). Half the difference, 0.10°, was added together: θ1' = 10.10 - 0.10 = 10.00°, θ2' = 9.90 + 0.10 = 10.00°. The corrected average rotation angle was 10.00°, consistent with the true value. Taking the arithmetic mean directly also yielded 10.00°, but the correction verified the symmetry of the two angles and provided a basis for subsequent data consistency judgment. Adding the corrected 10.00° to the initial opening angle of 5° for the single arm yielded the actual opening angle of 15.00°.

[0059] To illustrate the correction principle more intuitively, let the actual gear rotation angle be θtrue. The errors introduced by the eccentric installation of the magnet are +δ and -δ, respectively. Therefore, the two sensor readings can be expressed as θ1 = θtrue + δ, θ2 = θtrue - δ. At this point, the difference Δθ = 2δ, and the arithmetic mean θavg = (θ1 + θ2) / 2 = θtrue. The symmetrical correction process is: θ1' = θ1 - Δθ / 2 = θtrue + δ - δ = θtrue, θ2' = θ2 + Δθ / 2 = θtrue - δ + δ = θtrue. It can be seen that both corrected angles are equal to the true values, while retaining the original readings for anomaly detection.

[0060] This application achieves precise compensation for minute eccentricity errors by calculating the difference after averaging and performing symmetrical correction, while also establishing a self-diagnostic mechanism for equipment operation. When the difference exceeds the limit, an anomaly is promptly detected, preventing erroneous measurement data caused by sensor or mechanical failure from entering subsequent calculations, significantly improving the measurement reliability and environmental adaptability of the laser tree measuring instrument.

[0061] Furthermore, the method of installing the base handles of the two clamping arms through the same hinge shaft collar, so that the two base handles extend from the collar and are bent to form a horizontal cantilever section in the same plane, includes: designing the two base handles with different intermediate fold line lengths so that the two base handles extend in the same horizontal plane after bending; setting the angle bisector arm as a sliding structure so that it passes through an independent channel on the main housing and passes through the center of the hinge shaft of the two clamping arms, the bottom surface of which is higher than the plane where the two clamping arms are located; setting a downward bending structure at the front end of the angle bisector arm so that the front end contact of the angle bisector arm is pressed down and is in the same measuring plane as the front end contact of the two clamping arms.

[0062] Specifically, in this embodiment, both base shanks are integrally machined from 7075 aluminum alloy, and are mounted at the root via a hinged collar, with the center of the collar serving as a common pivot point. The left base shank has a first bend point 8mm horizontally from the collar center, a first bend angle of 45°, and a vertical extension of 12mm along the 45° direction after the first bend. The second bend angle is also 45°, and the horizontal extension after the second bend is 15mm. The right base shank has a first bend point 10mm horizontally from the collar center, a first bend angle of 45°, a vertical extension of 12mm along the 45° direction after the first bend, and a horizontal extension of 13mm after the second bend.

[0063] Calculate the height positions of the two horizontal cantilever sections based on the above parameters. The coordinates of the point reached after the first bend of the left base shank are (8 + 12×cos45°, 12×sin45°), i.e., (8 + 8.485, 8.485) = (16.485, 8.485). After the second bend, it extends horizontally by 15mm, and the final end coordinates are (16.485 + 15, 8.485) = (31.485, 8.485). The coordinates of the point reached after the first bend of the right base shank are (10 + 12×cos45°, 12×sin45°), i.e., (10 + 8.485, 8.485) = (18.485, 8.485). After the second bend, the horizontal extension is 13mm, and the final end coordinates are (18.485 + 13, 8.485) = (31.485, 8.485). The Y-coordinates of the ends of both horizontal cantilever segments are 8.485mm, achieving strict coplanarity.

[0064] After assembly, the vertical distance between the two horizontal cantilever sections and the plane containing the center of the collar was measured by a coordinate measuring machine. The vertical distance was 8.48mm ± 0.02mm, and the height difference between the two horizontal cantilever sections was less than 0.05mm.

[0065] It should be noted that the angle bisector arm is made of a flat strip of stainless steel, 8mm wide, 2mm thick, and 200mm long. An independent rectangular channel is machined into the main housing, with a cross-sectional dimension of 8.2mm wide and 5mm high. After the angle bisector arm is inserted into the channel, it can slide freely axially. The centerline of the channel passes through the center of the hinge axis of the two clamping arms, i.e., the center of the collar. The vertical distance between the bottom surface of the channel and the plane containing the two clamping arms is 5mm. When the angle bisector arm slides, its body plane is 5mm higher than the clamping arm plane, and there is no interference between them.

[0066] A downward bending structure is installed at the front end of the angle bisector arm, so that the front contact point of the angle bisector arm, after being pressed down, is in the same measuring plane as the front contact points of the two clamping arms. Specifically, the front end of the angle bisector arm is bent downwards at 90°, with a bending section length of 5mm. The end of the bending section serves as the contact point with the tree trunk. During assembly, a height gauge is used to measure the height of the front contact points of the two clamping arms. Based on the measurement results, the end face of the downward bending section is ground to ensure that the height difference between the angle bisector arm contact point and the two clamping arm contacts is less than 0.1mm. After testing, the final height difference of the three contacts is 0.05mm, and they are in the same measuring plane.

[0067] Through the above steps, the two clamping arms are strictly coplanar during the opening and closing process. At the same time, the angle bisector arm is also coplanar with the clamping arms, thus ensuring that when the three arms are in contact with the tree trunk, the measurement baseline is located in the same plane, eliminating the diameter measurement error caused by inconsistent contact point heights.

[0068] Furthermore, the step of setting magnets on the two sector gears respectively, and arranging Hall sensors in the main housing at positions corresponding to the magnets, includes: opening blind holes on the back of the non-meshing teeth of each sector gear, embedding and fixing the magnets in the blind holes; covering the surface of the magnets with insulating tape; setting plastic pillars inside the main housing, mounting sensor plates on the plastic pillars, and placing the Hall sensors on the sensor plates; adjusting the position of the sensor plates to create a gap between the Hall sensors and the magnets; and connecting the Hall sensors to the main housing via wires to transmit the detected electrical signals to the main housing.

[0069] Specifically, in this embodiment, the sector gear can be made of brass with a module of 0.3mm, 20 teeth, and a pitch circle radius of 3mm. A circular blind hole is machined on the back of the non-meshing side of the gear teeth, opposite to the meshing teeth, using a precision drilling machine. The blind hole has a diameter of 2.2mm and a depth of 1.8mm, with a smooth, burr-free bottom. A neodymium iron boron magnet of grade N52 is selected, with dimensions of 2.0mm × 2.0mm × 1.0mm and a cuboid shape. When embedding the magnet into the blind hole, the N pole faces outward and the S pole faces inward. A small amount of epoxy resin is used to fill the gap between the blind hole and the magnet. After the resin cures, the magnet is firmly fixed in place. Then, a layer of polyimide insulating tape (i.e., Kapton tape) is pasted on the surface of the magnet. The tape is 0.05mm thick, covering the entire exposed surface of the magnet and extending to the gear end face by about 1mm, to prevent the magnet from short-circuiting with external metal parts, while protecting the magnet from dust and moisture corrosion.

[0070] The main housing is injection molded from ABS plastic. Inside the housing, a cylindrical plastic pillar is positioned at the location corresponding to the rotational trajectories of the two magnets. The plastic pillars are integrally injection molded with the housing, with a diameter of 6mm and a height of 10mm, and a pre-drilled M2 threaded hole at the center of the top. The sensor board is made of FR4 epoxy fiberglass cloth, measuring 8mm × 8mm × 1mm, and has a pre-drilled 2.2mm diameter mounting through-hole and two solder pads. The pins of the linear Hall sensor (model SS495A) are inserted into the solder pads and fixed with solder, with the sensor's sensitive surface facing down. The sensor board is then fixed to the top of the plastic pillars using M2 × 8mm screws, ensuring the sensitive surface of the Hall sensor faces the magnets. The positions of the two plastic pillars are pre-defined using a mold, ensuring that when the clamping arms are closed, the two Hall sensors are essentially aligned with their corresponding magnets.

[0071] When fixing the sensor board, do not fully tighten the screws. Rotate the clamping arm to the closed position and use a feeler gauge to measure the distance between the sensitive surface of the Hall sensor and the surface of the magnet. Adjust the gap by moving the sensor board up and down, keeping the gap value within the range of 0.3mm ± 0.1mm. After adjustment, tighten the screws. Then, take three 0.1mm diameter enameled wires and solder them to the power (VCC), ground (GND), and output (OUT) pads on the sensor board, respectively. Pass the other end of the enameled wires through the wire groove inside the main unit housing and solder them to the corresponding interface on the main circuit board. The microcontroller on the main circuit board reads the analog voltage signal output by the Hall sensor through an analog-to-digital converter for subsequent angle calculation. To prevent the wires from loosening, apply a small amount of silicone to the wire groove for fixation.

[0072] Through the above steps, as the two magnets rotate with the sector gear, the gap between the Hall sensor and the magnets remains constant. The magnetic field strength generated by the magnets changes linearly with the angle, and the Hall sensor outputs a corresponding voltage signal. Actual measurements show that within a ±45° rotation range, the linearity between the output voltage and the rotation angle is better than 0.5%, providing a reliable raw signal for high-precision angle measurement.

[0073] Furthermore, the provision of an elastic connector between the bases of the two base handles further includes: selecting an elastic connector with different elastic coefficients according to the diameter range of the tree trunk to be tested; adjusting the preload of the elastic connector to an initial value that is compatible with the diameter range of the tree trunk, so that the clamping arm generates a normal clamping force when it is attached to the tree trunk, and the magnitude of the clamping force is positively correlated with the diameter of the tree trunk.

[0074] Specifically, in this embodiment, selecting elastic connectors with different elastic coefficients based on the diameter range of the tree trunk to be measured means equipping various specifications of tension springs for different measurement scenarios and tree species. Users can choose the appropriate spring according to the diameter range of the actual object being measured. In this embodiment, the laser tree measuring instrument is designed to measure tree trunks with diameters from 5cm to 50cm, dividing this range into three intervals: small diameter (5-15cm), medium diameter (15-30cm), and large diameter (30-50cm). Three different springs with varying elastic coefficients are selected for each of the three intervals: Spring A (elastic coefficient k1 = 0.3N / mm, suitable for small diameter); Spring B (elastic coefficient k2 = 0.6N / mm, suitable for medium diameter); and Spring C (elastic coefficient k3 = 1.0N / mm, suitable for large diameter). The free length of all three springs is 10mm, with wire diameters of 0.4mm, 0.5mm, and 0.6mm respectively, and a median diameter of 4mm for all. Before conducting field surveys, users select the appropriate spring based on the approximate diameter at breast height (DBH) range of the trees in the sample plot and install it between the lugs of the two base handles.

[0075] Adjusting the preload of the elastic connector to an initial value suitable for the trunk diameter range means adjusting the position of the spring lugs or adding shims to give the spring different initial stretches when the clamp arm is closed (10° angle between the two base handles), thus obtaining different initial preloads. In this embodiment, for spring A used in the small diameter range, when the lug position is adjusted to the closed state, the spring stretches to 11mm, with an elongation ΔL = 1mm, and the initial preload F0 = k1 × ΔL = 0.3 × 1 = 0.3N. For spring B used in the medium diameter range, adjusting the lugs so that the spring stretches to 12mm when closed, with an elongation ΔL = 2mm, and the initial preload F0 = 0.6 × 2 = 1.2N. For spring C used in the large diameter range, adjusting the lugs so that the spring stretches to 13mm when closed, with an elongation ΔL = 3mm, and the initial preload F0 = 1.0 × 3 = 3.0N.

[0076] The clamping arm generates a normal clamping force when it is attached to the tree trunk, and the magnitude of the clamping force is positively correlated with the diameter of the tree trunk. This means that when the clamping arm is opened to different angles to attach to tree trunks of different diameters, the spring is further stretched, the tension increases, and the normal clamping force transmitted to the front end of the clamping arm through gear meshing also increases. Moreover, the larger the diameter of the tree trunk, the greater the clamping force, ensuring that even large-diameter tree trunks can be firmly clamped.

[0077] Taking spring B (k=0.6N / mm, initial preload 1.2N) as an example, the normal clamping force under different trunk diameters is calculated. Assume the clamp arm length (from the center of the hinge collar to the trunk contact point) L=150mm, and the distance from the spring's point of action to the center of the collar d=25mm. The relationship between the trunk diameter D and the clamp arm's single-arm opening angle θ is: sinθ = D / (2L), therefore θ = arcsin(D / (2L)). When the clamp arm opens from the closed state (θ0=5°) to angle θ, the angle between the two base handles increases from 10° to 2θ. The relationship between the spring extension increment ΔLspring and the opening angle needs to be calculated based on geometric relationships. Through actual measurement and calibration, the relationship between the spring extension ΔLtotal and the single-arm opening angle θ is approximately ΔLtotal = initial extension + 0.2×(θ-5), in mm, and θ in degrees.

[0078] For a tree trunk with a diameter D = 10 cm: the single-arm opening angle θ = arcsin(100 / (2×150)) = arcsin(0.333) = 19.5°. The total spring tension ΔLtotal = 2 + 0.2×(19.5-5) = 2 + 0.2×14.5 = 2 + 2.9 = 4.9 mm. The spring force Fspring = k×ΔLtotal = 0.6×4.9 = 2.94 N. The normal clamping force Fnormal generated at the front end of the clamping arm by this tension is Fnormal = Fspring × d / L = 2.94 × 25 / 150 = 2.94 × 0.1667 = 0.49 N.

[0079] For a tree trunk with a diameter D = 20 cm: θ = arcsin(200 / (2×150)) = arcsin(0.667) = 41.8°. ΔLtotal = 2 + 0.2×(41.8-5) = 2 + 0.2×36.8 = 2 + 7.36 = 9.36 mm. Fspring = 0.6×9.36 = 5.62 N. Fnormal = 5.62 × 25 / 150 = 5.62 × 0.1667 = 0.94 N.

[0080] For a tree trunk with a diameter D = 30cm: θ = arcsin(300 / (2×150)) = arcsin(1) = 90°, but the actual maximum opening angle is limited to within 45°, so a diameter of 30cm is close to the upper limit. Taking θ = 45° for calculation: ΔLtotal = 2 + 0.2×(45-5) = 2 + 0.2×40 = 2 + 8 = 10mm. Fspring = 0.6×10 = 6.0N. Fnormal = 6.0× 25 / 150 = 6.0 × 0.1667 = 1.0N.

[0081] As the calculations above show, as the trunk diameter increases from 10cm to 30cm, the normal clamping force increases from 0.49N to 1.0N, achieving a positive correlation between clamping force and trunk diameter. This characteristic ensures that small-diameter trunks are not over-clamped and damaged, while large-diameter trunks can also obtain sufficient clamping force to ensure measurement stability.

[0082] Furthermore, this embodiment illustrates how to apply the aforementioned clamp arm angle measurement method to accurate carbon sequestration accounting. Using the above method, the actual opening angle α of the clamp arm is obtained through synchronous opening and closing of the clamp arm and angle measurement. According to... Figure 2 The geometric relationship shown is that the clamp arm length L is the distance from the hinge axis center A to the contact point at the front end of the clamp arm. In this embodiment, L = 150 mm. The trunk diameter D and the actual opening angle α of the clamp arm satisfy the relationship: D = 2L·sinα. In a certain measurement, the actual opening angle α of the clamp arm was calculated to be 25.00° through step S105. Substituting this into the formula, we get: D = 2 × 150 × sin25.00° = 300 × 0.4226 = 126.78 mm, that is, the diameter at breast height of the tree being measured is 12.68 cm.

[0083] Calculate the cross-sectional area A of the chest height based on the diameter at breast height (D): A = π × (D / 2)². Substituting D = 0.12678m into the equation, we get: A = 3.1416×(0.06339)² = 3.1416×0.004018 = 0.01262m².

[0084] The biomass per plant, B = a·D, is estimated using the allometric growth equation commonly used in forestry carbon sequestration. b Taking a certain broad-leaved tree species as an example, with a = 0.15 and b = 2.3, then: B = 0.15 × (12.68) 2.3 = 0.15 × 344.5 = 51.68kg.

[0085] Using the IPCC (Intergovernmental Panel on Climate Change) default carbon factor of 0.47, the carbon storage C = B × 0.47 is calculated as follows: C = 51.68 × 0.47 = 24.29 kg of carbon, meaning that the carbon storage of this single tree is 24.29 kg.

[0086] During the aforementioned measurement and calculation processes, the symmetrical correction mechanism of the dual Hall effect sensors ensured the accuracy of angle measurements, and the dynamic zero-point calibration eliminated the influence of environmental factors, providing reliable basic data for carbon sequestration accounting. Measurement results can be uploaded to the carbon sequestration database in real time via Bluetooth, enabling data traceability.

[0087] Secondly, this application also proposes a control system for the opening and closing of the clamping arm of a laser tree measuring instrument at the same angle, such as... Figure 4 As shown, it includes: The base handle mounting module 401 mounts the base handles of the two clamping arms through the same hinge shaft collar, so that the two base handles extend from the collar and are bent to form a horizontal cantilever section in the same plane. The gear transmission module 402 has a pair of involute sector gears with equal pitch circle radii fixed on the inner side of the root of the horizontal cantilever section of the two base shanks, so that the two gears mesh with each other to establish a one-to-one transmission relationship between the change of the clamping arm angle and the rotation of the gears. The elastic connection module 403 has an elastic connector between the bases of the two bases, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears. Angle detection module 404 has magnets on two sector gears respectively, and Hall sensors are arranged in the main housing at positions corresponding to the magnets, so that the two Hall sensors are distributed at a central angle of 180 degrees relative to the hinge axis. The angle calculation module 405 calculates the opening angle of the clamping arm based on the angle data detected by the Hall sensor.

[0088] This application also proposes a control system for the opening and closing of the clamping arms of a laser tree measuring instrument at the same angle. This system includes five modules. The base mounting module 401 is used to install the bases of the two clamping arms through the same hinge shaft collar, so that the two bases extend from the collar and are bent to form horizontal cantilever sections on the same plane. The gear transmission module 402 is used to fix a pair of involute sector gears with equal pitch circle radii to the inner side of the root of the horizontal cantilever section of the two bases, so that the two gears mesh with each other, establishing a one-to-one transmission relationship between the change in the clamping arm opening angle and the rotation of the gears. The elastic connection module 403 is used to set an elastic connector between the bases of the two bases, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears. The angle detection module 404 is used to set magnets on the two sector gears, and to arrange Hall sensors in the main housing at positions corresponding to the magnets, so that the two Hall sensors are distributed at a 180-degree central angle relative to the hinge shaft axis. The angle calculation module 405 is used to calculate the opening angle of the clamping arms based on the angle data detected by the Hall sensors. The modules described above work together to achieve synchronous opening and closing of the clamping arms and high-precision angle measurement. This system can be used to execute the method for achieving synchronous opening and closing of the laser tree measuring instrument clamping arms as described in the first aspect, which will not be elaborated further here.

[0089] Thirdly, this application also proposes a laser tree measuring instrument, including a laser tree measuring instrument clamp arm opening and closing control system as described in the second aspect; two clamp arms, each clamp arm including a base handle and a horizontal cantilever section; a main housing for accommodating the angle detection module and the angle calculation module; wherein the base handle is mounted to the main housing via a collar with the same hinge shaft, and the horizontal cantilever section extends from the collar and is bent, with the two horizontal cantilever sections side by side on the same horizontal plane.

[0090] Specifically, in this embodiment, the laser tree measuring instrument includes two clamping arms, each consisting of a base handle and a horizontal cantilever section. The base handle is mounted to the main housing via a hinge collar, allowing the two base handles to rotate around a common hinge axis. The base handle extends outward from the collar and undergoes two bends to form the horizontal cantilever section. The two horizontal cantilever sections are geometrically designed to be side-by-side in the same horizontal plane. This coplanar structure ensures that the clamping arms always move within the same plane during opening and closing, preventing torsional deformation. The main housing houses the angle detection module and angle calculation module of the aforementioned control system. The Hall sensor in the angle detection module is located inside the main housing, corresponding to the position of the magnet mounted on the sector gear; the angle calculation module is integrated on a circuit board inside the main housing, responsible for processing the electrical signals collected by the Hall sensor and calculating the opening angle of the clamping arms.

[0091] When this laser tree measuring instrument is in operation, the operator pulls open the clamping arms using a handle. The gear transmission module in the control system ensures that the two clamping arms open synchronously, the elastic connection module provides a stable clamping force, and the angle detection module collects angle data in real time, which is then processed by the angle calculation module to finally output the precise clamping arm opening angle, providing a benchmark for subsequent laser ranging. The entire device has a compact structure and is easy to operate, making it suitable for accurate carbon sequestration accounting in field forestry surveys.

[0092] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for achieving the same angle opening and closing of the clamping arm of a laser tree measuring instrument, characterized in that, include: The base shanks of the two clamping arms are installed through the same hinge collar, so that the two base shanks extend from the collar and are bent to form a horizontal cantilever section in the same plane. A pair of involute sector gears with equal pitch circle radii are fixed to the inner side of the root of the horizontal cantilever section of the two base shanks, so that the two gears mesh with each other to establish a one-to-one transmission relationship between the change of the clamping arm angle and the rotation of the gears. An elastic connector is provided between the bases of the two base shanks, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears. Magnets are set on the two sector gears respectively, and Hall sensors are arranged in the main housing at the corresponding positions of the magnets, so that the two Hall sensors are distributed at a central angle of 180 degrees relative to the hinge axis. The opening angle of the clamping arm is calculated based on the angle data detected by the Hall sensor.

2. The method for achieving the same angle opening and closing of the clamping arm of the laser tree measuring instrument according to claim 1, characterized in that, An elastic connector is provided between the bases of the two base shanks, such that the line of action of the tension of the elastic connector passes through the meshing point of the two gears, including: Adjust the position of the connection point of the elastic connector on the two base shanks so that the line of action of the tension of the elastic connector coincides with the common tangent of the meshing point of the two gears; When the two clamping arms are in the closed state, the tension of the elastic connector is transmitted through the gear meshing point, causing the two gears to generate a preload force that meshes with each other; When the operator pulls open the clamping arms, the meshing force at the gear meshing point and the tension of the elastic connector form a dynamic force balance, causing the two clamping arms to open synchronously. Once the clamping arms are in contact with the tree trunk, the tension of the elastic connector is transmitted through gear meshing to the normal clamping force of the two clamping arms on the tree trunk, and the clamping forces of the two clamping arms are equal in magnitude.

3. The method for achieving the same angle opening and closing of the clamping arm of the laser tree measuring instrument according to claim 2, characterized in that, Based on the angle data detected by the Hall sensor, the opening angle of the clamping arm is calculated, including: When the clamping arm is in the closed state, the output values ​​of the two Hall sensors are collected as the zero-point reference value; During the opening and closing of the clamping arm, the current output values ​​of the two Hall sensors are collected in real time, and the difference between the current output value and the zero-point reference value is calculated to obtain the rotation angle of the two gears. Calculate the arithmetic mean of the two rotation angles to obtain the average rotation angle of the gear; The actual opening angle of the clamp arm is obtained by adding the average rotation angle of the gear to the preset initial opening angle of the single arm.

4. The method for achieving the same angle opening and closing of the clamping arm of the laser tree measuring instrument according to claim 3, characterized in that, The step of collecting the output values ​​of two Hall sensors as zero-point reference values ​​when the clamping arm is in the closed state includes: During the device startup and initialization phase, the output values ​​of the two Hall sensors are collected in real time, and the rate of change of the output values ​​at adjacent sampling times is calculated. When the rate of change of the output values ​​of both Hall sensors is less than a preset threshold and the difference between the two output values ​​is less than a preset synchronization threshold, the clamp is determined to be in a stable closed state. The output values ​​of the two Hall sensors at this time are used as the zero-point reference values ​​respectively.

5. The method for achieving the same angle opening and closing of the clamping arm of the laser tree measuring instrument according to claim 4, characterized in that, After calculating the arithmetic mean of the two rotation angles to obtain the average rotation angle of the gear, the method further includes: Calculate the difference between the two rotation angles; when the difference exceeds the preset threshold, it is determined to be an abnormal gear meshing or Hall sensor failure, and an abnormal prompt message is output. When the difference is within the preset threshold range, half of the difference is superimposed on the two rotation angles respectively, and symmetrical correction is performed to obtain the corrected rotation angle, so as to eliminate the error caused by the eccentric installation of the magnet or the radial runout of the gear. The corrected rotation angle is added to the initial opening angle of the single arm to obtain the actual opening angle of the clamping arm.

6. The method for achieving the same angle opening and closing of the clamping arm of the laser tree measuring instrument according to claim 1, characterized in that, The method of installing the base shanks of the two clamping arms through the same hinge collar, so that the two base shanks extend from the collar and are bent to form a horizontal cantilever section in the same plane, includes: The two base shanks are designed with different intermediate fold line lengths so that the two base shanks extend out in the same horizontal plane after being bent. The angle bisector arm is configured as a sliding structure, allowing it to pass through an independent channel on the main housing and through the center of the hinge axis of the two clamping arms, with the bottom surface of the channel being higher than the plane containing the two clamping arms. A bending structure is set at the front end of the angle bisector arm so that the front contact of the angle bisector arm is pressed down and is in the same measuring plane as the front contact of the two clamping arms.

7. The method for achieving the same angle opening and closing of the clamping arm of the laser tree measuring instrument according to claim 1, characterized in that, Magnets are respectively installed on the two sector gears; The arrangement of the Hall sensor within the main housing at a position corresponding to the magnet includes: A blind hole is made on the back of the non-meshing side teeth of each sector gear, and a magnet is embedded in the blind hole for fixation; insulating tape is then covered on the surface of the magnet. A plastic pillar is set inside the main housing, a sensor board is installed on the plastic pillar, and the Hall sensor is set on the sensor board. Adjust the position of the sensor board to create a gap between the Hall sensor and the magnet; the Hall sensor is connected to the host via a wire and transmits the detected electrical signal to the host.

8. The method for achieving the same angle opening and closing of the clamping arm of the laser tree measuring instrument according to claim 2, characterized in that, The provision of an elastic connector between the bases of the two base handles further includes: Based on the diameter range of the tree trunk to be tested, select elastic connectors with different elastic coefficients; The preload of the elastic connector is adjusted to an initial value that is compatible with the trunk diameter range, so that the clamping arm generates a normal clamping force when it is attached to the trunk, and the magnitude of the clamping force is positively correlated with the trunk diameter.

9. A control system for the same-angle opening and closing of the clamping arm of a laser tree measuring instrument, characterized in that, include: The base shank mounting module installs the base shanks of the two clamping arms through the same hinged collar, so that the two base shanks extend from the collar and are bent to form a horizontal cantilever section on the same plane. The gear transmission module has a pair of involute sector gears with equal pitch circle radii fixed on the inner side of the root of the horizontal cantilever section of the two base shanks, so that the two gears mesh with each other to establish a one-to-one transmission relationship between the change of the clamping arm angle and the rotation of the gears. The elastic connection module has an elastic connector between the bases of the two bases, so that the line of action of the tension of the elastic connector passes through the meshing point of the two gears. The angle detection module has magnets on two sector gears and Hall sensors arranged in the main housing at positions corresponding to the magnets, so that the two Hall sensors are distributed at a 180-degree central angle relative to the hinge axis. The angle calculation module calculates the opening angle of the clamping arm based on the angle data detected by the Hall sensor.

10. A laser tree measuring instrument, characterized in that, Includes the same-angle opening and closing control system for the laser tree measuring instrument clamp arm as described in claim 9; Two clamping arms, each clamping arm comprising a base shank and a horizontal cantilever section; The main unit housing is used to house the angle detection module and the angle calculation module; The base shank is mounted to the main housing via the same hinged collar, and the horizontal cantilever section extends from the collar and is bent, with the two horizontal cantilever sections side by side on the same horizontal plane.

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