Decoupling method of integrated six-dimensional force sensor for combine harvester

Abstract

The invention discloses a decoupling method of an integrated six-dimensional force sensor for a combine harvester, and belongs to the technical field of sensor application. The sensor adopts a Y-shaped three-beam radial symmetric structure, and highly integrates a belt wheel function and a six-dimensional force detection function: establishing an elastomer structure simplified mechanical model, establishing a semi-analytical method model, and analyzing to obtain a strain distribution rule under a uniaxial load. Acquiring a sensor geometric structure and a strain gauge measurement position which meet design requirements according to a strain distribution rule; a multi-output least square support vector regression machine is adopted, hyper-parameters are optimized through grid search, a high-precision mapping model from an electric signal to a six-dimensional load is constructed, the decoupling precision is greatly improved, the whole process innovation from the structure to stress analysis to decoupling is realized, and the method is suitable for large-scale popularization and application. The device is especially suitable for agricultural machinery scenes with limited space and complex load, such as combine harvesters.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sensor application, and particularly relates to a decoupling method of an integrated six-dimensional force sensor for a combine harvester. BACKGROUND

[0002] During operation, agricultural machinery such as a combine harvester bears complex dynamic loads on the transmission system, including radial force, axial force, and torque. Accurate monitoring of these loads is of great significance for optimizing mechanical performance, preventing component failure, and improving operation efficiency. Traditional measurement methods usually use external force sensors or torque sensors, but due to the compact structure of agricultural machinery and the harsh working environment (such as large vibration, much dust, high humidity, etc.), the installation of external sensors is often limited by space and is easily disturbed by the outside environment, resulting in a decrease in measurement accuracy.

[0003] Currently, six-dimensional force sensors are widely used in robotics, automobiles, medical and aerospace industries, which can directly measure the transformation of forces in XYZ three directions in space and the size of torque, and have the advantages of small size, compact structure, and low cost, but their application in the field of agricultural machinery still has the following problems: 1. Existing six-dimensional force sensors are mostly independent of the transmission components and cannot be directly integrated into the belt wheel mechanism of the combine harvester, requiring additional space for installation, which is difficult for compact harvester structures to spare.

[0004] 2. It is difficult to meet the long-term stable working requirements in terms of anti-vibration and dust prevention in the face of complex working conditions of agricultural machinery.

[0005] 3. The strain analysis model of traditional sensors may not accurately reflect the actual load distribution of the harvester belt wheel. SUMMARY

[0006] The application provides a decoupling method of an integrated six-dimensional force sensor for a combine harvester to solve the technical problems in the background art.

[0007] The application adopts the following technical solution: a decoupling method of an integrated six-dimensional force sensor for a combine harvester, comprising the following steps: Design an integrated six-dimensional force sensor with a belt wheel and a six-dimensional sensor, the integrated six-dimensional force sensor comprising: a center table, a plurality of groups of elastic beams fixed on the outer side of the center table in the radial direction; obtain the physical parameter information of the integrated six-dimensional force sensor and simplify to obtain a sensor mechanics model; By separately applying multi-directional loads to the integrated six-dimensional force sensor, the stress distribution or strain distribution of each group of elastic beams is analyzed; Based on the stress distribution or strain distribution of each group of elastic beams, the installation scheme of a plurality of stress sheets is verified to determine the optimal installation position of each group of elastic beams, and the corresponding stress sheet is installed; A preset six-dimensional load is applied to the integrated six-dimensional force sensor, and the output signals of each group of stress sheets are collected in real time. The output signals are denoised to obtain processed electrical signals; A six-dimensional output model of the integrated six-dimensional force sensor is constructed, the processed electrical signals are input based on the six-dimensional output model, and the actual six-dimensional load borne by the integrated six-dimensional force sensor is output, and the decoupling is completed.

[0008] In further embodiments, the sensor mechanics model is obtained as follows: Establish a local coordinate system : the center of the center table as the origin, the x-axis outward along the AB beam axis, the y-axis in the plane and the x-axis at an angle, the z-axis perpendicular to the plane; the load satisfies the following spatial conversion relationship between the global rectangular coordinate system and the local coordinate system : wherein, is the six-dimensional load vector in the global rectangular coordinate system , is the six-dimensional load vector in the local coordinate system , is the load conversion matrix; Based on the physical parameter information, a sensor mechanics model in the local coordinate system is established, and its expression form is as follows: ; wherein, L is the length of the elastic beam, ; , and are the cross-sectional width, cross-sectional area and moment of inertia of the elastic beam at ; and are the inner width and outer width of the elastic beam, is the height of the elastic beam; Based on the spatial conversion relationship, the six-dimensional load vector in the global rectangular coordinate system is obtained from the six-dimensional load vector in the local coordinate system .

[0009] In a further embodiment, the elastic beams are in three groups, evenly distributed along the circumference to form a Y-shaped structure; Define one elastic beam in the Y-shaped structure as beam AB, and the elastic beams on both sides of beam AB as beams CD and EF, respectively. The multi-directional loads include: Force in the axial direction , Force in the axial direction , around Torque of the shaft and around Moment in the axial direction .

[0010] In a further embodiment, when the load is Force in the axial direction The stress and strain distributions of beam AB are then analyzed using the following steps: Establish the stress-deflection of beam AB Series form and rotation The stress deflection is in the form of a series. Series form and rotation The series form contains the deflection series coefficients to be determined. and the coefficient of the series of turns ; Deflection under stress Series form and rotation Substituting the numerical form into the force-geometric relationship of beam AB, the equations are reduced to a system of algebraic equations using the weighted residual method, and then simplified to matrix form by considering the boundary conditions. Where H is the coefficient matrix and C is the unknown vector containing the deflection series coefficients. and the coefficient of the series of turns F is the load vector; Deflection series coefficients are solved using Gaussian elimination. and the coefficient of the series of turns And calculate the stress on beam AB. Bending stress at time and shear stress : , ;in, for The width of the cross section at that location, L is the height of the elastic beam, and L is the length of the elastic beam. elastic beam in The cross-sectional area at that point, For elastic beams Shear strain at the point, This is the shear correction factor; corresponding to the bending strain and the shear strain of the AB beam under force : , wherein, E is the elastic modulus of the material, G is the shear modulus of the material.

[0011] In further embodiments, based on the structural relationship of the AB beam and the EF beam, the strain distribution of the EF beam is analyzed by the following steps: Based on the AB beam, the force balance equation of the EF beam is established: wherein, and are the forces on the E end of the EF beam and the A end of the AB beam; At the same time, the initial disturbance relationship of the AB beam and the EF beam is established: , is the deflection of the AB beam under force, is the equation coefficient; The constraint force on the E end of the EF beam is orthogonally decomposed into the axial force component and the tangential force component , and based on the geometric relationship balance equation of the EF beam, the equation coefficients and the tangential force component are solved; The strain of the EF beam is obtained by the following formula: : , E is the elastic modulus of the material, A is the cross-sectional area of the elastic beam at .

[0012] In further embodiments, when the load is axial force , based on the structural relationship of the AB beam, the CD beam and the EF beam, the following steps are performed to obtain the stress distribution and strain distribution of each group of beams: The force balance relationship of the AB beam, the CD beam and the EF beam is established: ; wherein, , , are the forces on the A end, the C end and the E end of the AB beam, the CD beam and the EF beam, respectively; Based on the force balance relationship, the bending strain and the shear strain of each group of beams are solved, i.e. the strain distribution of each group of beams; Correspondingly, the bending stress and the shear stress : , is the elastic modulus of the material; , is the shear modulus of the material.

[0013] In further embodiments, when the load is a torque about the axis , the stress distribution and strain distribution of the AB beam are analyzed by the following steps: calculating the section torsion coefficient of the AB beam at any position : wherein, is the shape coefficient, is the section width at , is the height of the elastic beam; based on the section torsion coefficient , the shear force of the AB beam at any position is calculated: : ; combining the section torsion coefficient and the shear force , the longitudinal strain and the normal strain of the AB beam are obtained: , is the corresponding beam height at any position of the AB beam; , represents the Poisson's ratio of the beam material; correspondingly, the normal stress of the AB beam in the axis direction is : , is the elastic modulus of the material; the normal stress of the AB beam in the axis direction is : .

[0014] In further embodiments, based on the structural relationship between the AB beam and the EF beam, the stress distribution and strain distribution of the EF beam are analyzed by the following steps: establishing the force balance equation between the AB beam, the CD beam and the EF beam: wherein, is the torque borne by the AB beam, is the counter-restraint force of the C end of the CD beam, ​is the radius of the center table; According to the geometric relationship between the AB beam, the CD beam and the EF beam, the force relationship is established: , is the force of the AB beam, is the force of the C end and the E end of the CD beam and the EF beam respectively, is the resultant force; Combining the force balance equation, the solution is obtained : ; Therefore, the strain of the CD beam and the EF beam is : , is the cross-sectional area at ; The stress of the CD beam and the EF beam is : .

[0015] In further embodiments, when the load is a torque around the axis, the forces of the AB beam, the CD beam and the EF beam are the same, taking the beam AB as the analysis object, the stress distribution and the strain distribution of the AB beam are analyzed by the following steps: Based on the torque balance principle, the counter torque of the outer single of the AB beam is determined, and the cross-sectional bending moment at any position of the AB beam is determined; The bending strain and the shear strain of the AB beam are calculated by the following formula: , is the corresponding beam height at any position of the AB beam, is the material elastic modulus, is the cross-sectional moment of inertia of the AB beam around the z axis, and G is the shear modulus of the material, is the cross-sectional area at , is the shear correction coefficient; The bending normal stress and the shear stress are calculated based on the bending strain and the shear strain respectively: , .

[0016] In further embodiments, the construction process of the six-dimensional output model comprises: Using the processed electrical signal as input data, variable selection is performed on the input data to identify feature variables that are highly correlated with load prediction and use them as input features to form a training sample set. The preset six-dimensional loads corresponding to the input features are used as output data to form the output matrix. ; For the training sample set and output matrix Standardize them separately to obtain standardized training sample sets. and standardized output matrix , Based on the support vector regression model, with a standardized training sample set and standardized output matrix Based on this, a load prediction model is built, and the kernel function of the load prediction model is created. The kernel function The expression is as follows: ,in, It is the first and the One input sample, This is the kernel function width parameter; A grid search method is used to perform a search on the kernel function width parameter. Optimize the kernel width parameter until the performance of the load prediction model is optimal. ; The mapping relationship between the processed electrical signal and the load borne by the integrated six-dimensional force sensor is determined, and the six-dimensional output model of the integrated six-dimensional force sensor is obtained.

[0017] The beneficial effects of this invention are as follows: This invention integrates the pulley and the six-dimensional sensor into a single structure. Compared to the traditional separate "sensor and pulley" design, this significantly reduces the gaps between components and assembly errors, effectively avoiding load measurement deviations caused by vibration and impact during combine harvester operations (such as grain harvesting and straw crushing). Simultaneously, the three sets of elastic beams (Y-shaped structure) evenly distributed radially along the central platform can evenly bear loads in multiple directions. For example: Force in the axial direction , Force in the axial direction , around Torque of the shaft and around Moment in the axial direction It adapts to the complex stress environment of combine harvester pulleys, improving the overall structural stability and service life of the sensor.

[0018] This invention establishes a local coordinate system. The load conversion relationship between the local rectangular coordinate system and the global rectangular coordinate system is constructed, a mechanical model conforming to the actual structure of the sensor is constructed, and theoretical errors caused by a simplified model are avoided, thereby providing accurate mechanical basis for subsequent load decoupling.

[0019] The present application verifies and determines the optimal installation position of the strain gauge by analyzing the stress distribution and strain distribution of each group of elastic beams, effectively avoiding the interference of stress concentration or weak strain area on the measurement signal. At the same time, based on the strain law under multi-directional load, the strain gauge is installed, which can accurately capture the difference of strain signals corresponding to different loads, lay a foundation for subsequent differentiation of six-dimensional load and reduction of signal cross interference, and improve the measurement sensitivity of the sensor to the complex load of the combine harvester.

[0020] The present application processes the collected strain gauge output signal, combines the standardized training sample and the support vector regression model (SVR), constructs a six-dimensional output model, and optimizes the kernel function parameters through grid search, so as to ensure that the model can accurately establish the mapping relationship between the processed electrical signal and the actual six-dimensional load. Compared with the traditional decoupling method (such as linear fitting), the model can effectively process the coupling effect between loads, and even in the dynamic operation scene of the combine harvester (such as load mutation and multi-load superposition), it can also quickly output accurate six-dimensional load data, and provide reliable data support for operation parameter optimization (such as feed rate adjustment and cutter speed control) and fault warning (such as bearing wear monitoring) of the combine harvester. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a flowchart of the decoupling method of the integrated six-dimensional force sensor for the combine harvester.

[0022] Figure 2 It is a structural schematic diagram of the integrated six-dimensional force sensor.

[0023] Figure 3 It is a relationship diagram between the local rectangular coordinate system and the global rectangular coordinate system.

[0024] Figure 4 It is a mechanical model diagram of the sensor.

[0025] Figure 5 It is a three-view diagram of the beam AB.

[0026] Figure 6 It is a force diagram of the elastic beam.

[0027] Figure 7 It is an intuitive principle diagram of the MLS-SVR.

[0028] Figure 8 It is a K-fold cross-validation principle diagram.​​​

[0029] Figure 2 The labels in the text are: outer shell 1, elastic beam 2, center platform 3, mounting groove 4, double belt groove structure 101. Detailed Implementation

[0030] The present invention will now be further described with reference to the accompanying drawings and embodiments.

[0031] Example 1 like Figure 1 As shown, the decoupling method for an integrated six-dimensional force sensor for combine harvesters includes the following steps: Design an integrated six-dimensional force sensor that combines a pulley and a six-dimensional sensor. The integrated six-dimensional force sensor includes: a central platform and several sets of elastic beams fixed radially to the outer side of the central platform; acquire the physical parameter information of the integrated six-dimensional force sensor and simplify it to obtain the sensor's mechanical model. By applying multi-directional loads individually to an integrated six-dimensional force sensor, the stress or strain distribution of each elastic beam is analyzed. Based on the stress or strain distribution of each group of elastic beams, the installation schemes of several stress plates are verified to determine the optimal installation position of each group of elastic beams and to install the corresponding stress plates. A preset six-dimensional load is applied to the integrated six-dimensional force sensor, and the output signal of each stress plate is collected in real time. The output signal is then denoised to obtain the processed electrical signal. A six-dimensional output model of an integrated six-dimensional force sensor is constructed. Based on the processed electrical signal input to the six-dimensional output model, the actual six-dimensional load borne by the integrated six-dimensional force sensor is output, thus completing the decoupling.

[0032] Furthermore, in combination Figures 2 to 5 The integrated six-dimensional force sensor involved in this embodiment has the following specific structure: the elastic beam consists of three groups, which are evenly distributed along the circumference to form a Y-shaped structure.

[0033] In the Y-shaped structure, one elastic beam is defined as beam AB, and the elastic beams on either side of beam AB are beams CD and EF, respectively. A mounting groove is provided at a designated position on each beam for mounting stress plates. In this embodiment, the center platform, elastic beams, and outer shell are made of alloy material; the mounting grooves are obtained through a quenching process.

[0034] like Figure 2 As shown, it includes an outer shell 1, an elastic beam 2, and a central platform 3. The main structure of the outer shell 1 is annular and has a double belt groove structure 101. The main structure of the elastic beam 2 is trapezoidal and has a square mounting groove 4 in the middle. The main structure of the central platform 3 is annular.

[0035] The six-dimensional force sensor of this invention is installed on the pulley in the outer transmission device of the harvester, directly replacing the original pulley. It is fitted through a 50mm diameter inner hole in the center plate and a 300mm diameter pulley groove in the outer housing for belt mounting. After installation, the sensor receives signals wirelessly, satisfying the harvester pulley requirements while also functioning as a sensor. Strain gauges attached to the square strain gauge grooves on the elastic beam form a strain gauge group, used to detect the load on the sensor and output an electrical signal.

[0036] For the sensors installed on the harvester, strain analysis of each elastic beam can be performed directly using force analysis methods. Based on the magnified view of the six-dimensional force sensor, the geometric dimensions of each part of the structure are defined, and the mechanical model is simplified; beam length... Beam height Left side width Right side width Elastic modulus shear modulus .

[0037] Firstly, to ensure the accuracy between the model and the actual object, combined with Figure 3 The process of obtaining the sensor's mechanical model is as follows: Establish a local coordinate system Taking the center of the central platform as the origin, The axis extends outward along the axial direction of beam AB. Axis in In-plane and Axis horn, Axis perpendicular to Surface; load in global rectangular coordinate system and local coordinate system The following spatial transformation relationship is satisfied between them: ,in, global rectangular coordinate system The six-dimensional load vector below, Local coordinate system The six-dimensional load vector below, This is the load transformation matrix; Establish a local coordinate system based on physical parameter information. The sensor's mechanical model is expressed as follows: ; Where L is the length of the elastic beam, ; , and Each is an elastic beam in The cross-sectional width, cross-sectional area and moment of inertia of the elastic beam; and respectively the inner end width and the outer end width of the elastic beam, is the height of the elastic beam; Based on the spatial conversion relationship, the six-dimensional load vector in the global rectangular coordinate system is obtained through the six-dimensional load vector in the local coordinate system .

[0038] In combination Figure 3 , taking the six-axis load as an example, is the six-dimensional load vector in the global rectangular coordinate system, wherein, , , and are respectively the forces along the axis, , and are respectively the moments of force around the axis; is the six-dimensional load vector in the local coordinate system, , , , and are respectively the forces along the axis, , and are respectively the moments of force around the axis; is the load conversion matrix, ; wherein, is the included angle between the axis, axis, and in the embodiment .

[0039] By adopting the above technical solution, the stress and strain analysis of a single elastic beam is ensured to be accurate by using the local model, and the load conversion matrix integrates the local stress of multiple elastic beams into the global six-dimensional load, and the combination of the two provides a unified mechanical reference for the subsequent “strain gauge installation position verification” and “six-dimensional output model construction”, avoids the decoupling error caused by the ambiguity of the local and global load correspondence, and lays a key theoretical foundation for the final realization of the six-dimensional load accurate measurement of the sensor.

[0040] ​Therefore, the position of the installation groove is very important, so in the embodiment, stress distribution or strain distribution of each group of elastic beams is analyzed by separately applying multi-directional loads to the integrated six-dimensional force sensor; based on the stress distribution or strain distribution of each group of elastic beams, the installation scheme of several stress sheets is verified to determine the optimal installation position of each group of elastic beams, and the corresponding stress sheet is installed. Since the mechanical simplified model of the elastic structure is established in the above strain analysis and calculation, according to the Saint-Venant principle, the strain of the elastic beam end under the load condition is not accurate, and at the same time, the strain of the end region is complex in combination with the actual situation, so the middle position of the beam is selected for slotting and pasting the strain sheet to obtain relatively stable and reliable strain data.

[0041] For example, the multi-directional load of the embodiment includes: Figure 6 axial force , axial force , torque around axis , and torque around axial direction .

[0042] Further, when the load is axial force , the stress distribution and strain distribution of the AB beam are analyzed by the following steps: establishing the force deflection series form and the rotation angle series form of the AB beam, wherein the force deflection series form and the rotation angle series form respectively contain the deflection series coefficient and the rotation angle series coefficient to be solved.

[0043] Specifically: , ; wherein, represents an arbitrary position of the beam, and are deflection series base functions and rotation angle series base functions respectively, is the number of expansion terms of the series, .

[0044] wherein the deflection series base function and the rotation angle series base function are respectively represented as: , .

[0045] the force deflection series form and the rotation angle ​Substituting the numerical form into the geometric force relationships of beam AB, The weighted residual method transforms the equations into a system of algebraic equations, which are then simplified into matrix form by considering the boundary conditions. Where H is the coefficient matrix and C is the unknown vector containing the deflection series coefficients. and the coefficient of the series of turns F is the load vector.

[0046] In this embodiment, the boundary conditions are simplified to conditions on deflection. Bending moment and shear force The simplification, that is, when and The corresponding value at that time.

[0047] Deflection series coefficients are solved using Gaussian elimination. and the coefficient of the series of turns And calculate the stress on beam AB. Bending stress at time and shear stress : , ;in, for The width of the cross section at that location, L is the height of the elastic beam, and L is the length of the elastic beam. elastic beam The cross-sectional area at that point, For elastic beams Shear strain at the point, This is the shear correction factor; Correspondingly, the stress on beam AB is obtained. Bending strain and shear strain : , ,in, The elastic modulus of the material. This is the shear modulus of the material.

[0048] Because the sensor has a symmetrical structure, beams CD and EF are symmetrical and subjected to the same forces. The deformation and strain of beams CD and EF are the same. We will take beam EF as an example.

[0049] Based on the structural relationship between beams AB and EF, the stress distribution of beam EF is obtained through the following steps: Based on beam AB, establish the force equilibrium equations for beam EF: ,in, and It refers to the forces acting on end E of beam EF and end A of beam AB; Simultaneously, establish the initial deflection relationship between beams AB and EF: , It is the stress-induced deflection of beam AB. These are the equation coefficients; The constraint forces at end E of beam EF are orthogonally decomposed into axial force components. and tangential force components Based on the geometric equilibrium equations of beam EF, the equation coefficients were obtained by solving the equations. and axial force components ; The strain of beam EF is obtained using the following formula. : , The elastic modulus of the material. elastic beam in The cross-sectional area at that point.

[0050] In another embodiment, when the load is Force in the axial direction Based on the structural relationships of beams AB, CD, and EF, the following steps are performed to obtain the stress and strain distributions for each group of beams: Establish the force equilibrium relationships for beams AB, CD, and EF: ;in, , , These represent the forces acting on ends A, C, and E of beams AB, CD, and EF, respectively. Based on the aforementioned force equilibrium relationship, the bending strain of each group of beams is calculated. With shear strain That is, the strain distribution of each group of beams; The bending stress of each group of beams is obtained accordingly. and shear stress : , The elastic modulus of the material; , This is the shear modulus of the material.

[0051] In another embodiment, when the load is a winding Torque of the shaft The stress and strain distributions of beam AB are then analyzed using the following steps: Calculate the position of beam AB at any location. Torsional coefficient at the section : ,in, The shape factor, for The cross-sectional width at the position of the AB beam, The height of the elastic beam; Based on the cross-sectional torsion coefficient The shear force at any position of the AB beam : : ; The longitudinal strain of the AB beam is obtained by combining the cross-sectional torsion coefficient and the shear force : and the positive strain : , The corresponding beam height at any position of the AB beam : , The material Poisson's ratio of the beam; The corresponding, AB beam The positive stress in the axial direction is : , The material elastic modulus; AB beam The positive stress in the axial direction is : .

[0052] Based on this, for the CD beam and EF mechanical energy force analysis, the stress distribution and strain distribution of the EF beam are obtained by the following steps: Establish the force balance equation between the AB beam, CD beam and EF beam: where, is the moment of force borne by the AB beam, is the counter-restraint force at the C end of the CD beam, is the radius of the center table; According to the geometric relationship between the AB beam, CD beam and EF beam, the force relationship is established: , is the force of the AB beam, is the force at the C end and E end of the CD beam and EF beam respectively, is the resultant force; Combining the force balance equation, the solution is obtained : ; Then, the strain of the CD beam and the EF beam is : , is the cross-sectional area at the position of ; The stress of the CD beam and the EF beam is : .

[0053] In another embodiment, when the load is a winding Torque of the shaft At that time, beams AB, CD, and EF are subjected to the same forces. Taking beam AB as the analysis object, the stress and strain distribution of beam AB are obtained through the following steps: Based on the principle of torque balance, determine the counter torque of the outer single beam of beam AB. And at any position along the axial direction of beam AB Bending moment at section ; The bending strain of beam AB is calculated using the following formula. and shear strain : , For any position of beam AB The corresponding beam height, The elastic modulus of the material. Let G be the moment of inertia of beam AB about the z-axis, and G be the shear modulus of the material. yes The cross-sectional area at that point, This is the shear correction factor; Based on the bending strain and shear strain The bending normal stress was calculated separately. and shear stress : , .

[0054] Finally, this embodiment also discloses the construction process of the six-dimensional output model, including: Using the processed electrical signal as input data, variable selection is performed on the input data to identify feature variables that are highly correlated with load prediction and use them as input features to form a training sample set. The preset six-dimensional loads corresponding to the input features are used as output data to form the output matrix. ; For the training sample set and output matrix Standardize them separately to obtain standardized training sample sets. and standardized output matrix The standardization process described in this embodiment can be the Z-Score standardization method.

[0055] Combination Figure 7 Based on the support vector regression model, using a standardized training sample set and standardized output matrix Building a load prediction model based on the kernel function of the load prediction model The expression form of the kernel function is as follows: wherein, is the first and the second input sample, is the kernel function width parameter; The grid search method is used to optimize the kernel function width parameter until the kernel function width parameter that makes the performance of the load prediction model optimal is obtained ; the average performance index of the model is evaluated using K-fold cross-validation. As shown in Figure 8 , this embodiment uses 4-fold cross-validation to find the hyperparameters that minimize the mean square error (MSE) and maximize the determination coefficient (R 2 ).

[0056] The mapping relationship between the processed electrical signal and the load borne by the integrated six-dimensional force sensor is determined, and the six-dimensional output model of the integrated six-dimensional force sensor, i.e., the output borne load value , , , , , , is obtained, and decoupling is completed.

[0057] The corresponding relationship between the electrical signal measured by the strain gauge group and the force or torque borne by the calibration test sensor is the six-dimensional output model of the six-dimensional force sensor, decoupling is performed, and the decoupling results are shown in Table 1.

[0058] Table 1 Based on the decoupling results of the experimental measurement data by the multi-output least square support vector regression, the effect is excellent, and the coupling problem between the signals of the six-dimensional force sensor can be well solved, and the measurement accuracy is improved.

[0059] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details, nor limit the specific embodiments of the application. The embodiments are selected and described in the specification in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited by the claims and their entire scope and equivalents.

Claims

1. A decoupling method for an integrated six-dimensional force sensor for combine harvesters, characterized in that, Includes the following steps: Design an integrated six-dimensional force sensor that combines a pulley and a six-dimensional sensor. The integrated six-dimensional force sensor includes: a central platform and several sets of elastic beams fixed radially to the outer side of the central platform; acquire the physical parameter information of the integrated six-dimensional force sensor and simplify it to obtain the sensor's mechanical model. By applying multi-directional loads individually to an integrated six-dimensional force sensor, the stress or strain distribution of each elastic beam is analyzed. Based on the stress or strain distribution of each group of elastic beams, the installation schemes of several stress plates are verified to determine the optimal installation position of each group of elastic beams and to install the corresponding stress plates. A preset six-dimensional load is applied to the integrated six-dimensional force sensor, and the output signal of each stress plate is collected in real time. The output signal is then denoised to obtain the processed electrical signal. A six-dimensional output model of an integrated six-dimensional force sensor is constructed. Based on the processed electrical signal input to the six-dimensional output model, the actual six-dimensional load borne by the integrated six-dimensional force sensor is output, thus completing the decoupling.

2. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 1, characterized in that, The process of obtaining the sensor's mechanical model is as follows: Establish a local coordinate system Taking the center of the central platform as the origin, The axis extends outward along the axial direction of beam AB. Axis in In-plane and Axis horn, Axis perpendicular to Surface; load in global rectangular coordinate system and local coordinate system The following spatial transformation relationship is satisfied between them: ,in, global rectangular coordinate system The six-dimensional load vector below, Local coordinate system The six-dimensional load vector below, This is the load transformation matrix; Establish a local coordinate system based on physical parameter information. The sensor's mechanical model is expressed as follows: ； Where L is the length of the elastic beam, ; , and Each is an elastic beam in The width, area, and moment of inertia of the cross-section at that location; and These are the inner and outer widths of the elastic beam, respectively. The height of the elastic beam; Based on the aforementioned spatial transformation relationship, through the local coordinate system The six-dimensional load vector below is used to obtain the global rectangular coordinate system. The six-dimensional load vector below.

3. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 1, characterized in that, The elastic beams are in three groups, evenly distributed along the circumference to form a Y-shaped structure; Define one elastic beam in the Y-shaped structure as beam AB, and the elastic beams on both sides of beam AB as beams CD and EF, respectively. The multi-directional loads include: Force in the axial direction , Force in the axial direction , around Torque of the shaft and around Moment in the axial direction .

4. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 1, characterized in that, When the load is Force in the axial direction The stress and strain distributions of beam AB are then analyzed using the following steps: Establish the stress-deflection of beam AB Series form and rotation The stress deflection is in the form of a series. Series form and rotation The series form contains the deflection series coefficients to be determined. and the coefficient of the series of turns ; Deflection under stress Series form and rotation Substituting the numerical form into the force-geometric relationship of beam AB, the equations are reduced to a system of algebraic equations using the weighted residual method, and then simplified to matrix form by considering the boundary conditions. Where H is the coefficient matrix and C is the unknown vector containing the deflection series coefficients. and the coefficient of the series of turns F is the load vector; Deflection series coefficients are solved using Gaussian elimination. and the coefficient of the series of turns And calculate the stress on beam AB. Bending stress at time and shear stress : , ;in, for The width of the cross section at that location, L is the height of the elastic beam, and L is the length of the elastic beam. elastic beam in The cross-sectional area at that point, For elastic beams Shear strain at the point, This is the shear correction factor; Correspondingly, the stress on beam AB is obtained. Bending strain and shear strain : , ,in, The elastic modulus of the material. This is the shear modulus of the material.

5. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 4, characterized in that, Based on the structural relationship between beams AB and EF, the strain distribution of beam EF is obtained through the following steps: Based on beam AB, establish the force equilibrium equations for beam EF: ,in, and It refers to the forces acting on end E of beam EF and end A of beam AB; Simultaneously, establish the initial deflection relationship between beams AB and EF: , It is the stress-induced deflection of beam AB. These are the equation coefficients; The constraint forces at end E of beam EF are orthogonally decomposed into axial force components. and tangential force components Based on the geometric equilibrium equations of beam EF, the equation coefficients were obtained by solving the equations. and axial force components ; The strain of beam EF is obtained using the following formula. : , The elastic modulus of the material. elastic beam in The cross-sectional area at that point.

6. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 1, characterized in that, When the load is Force in the axial direction Based on the structural relationships of beams AB, CD, and EF, the following steps are performed to obtain the stress and strain distributions for each group of beams: Establish the force equilibrium relationships for beams AB, CD, and EF: ;in, , , These represent the forces acting on ends A, C, and E of beams AB, CD, and EF, respectively. Based on the aforementioned force equilibrium relationship, the bending strain of each group of beams is calculated. With shear strain That is, the strain distribution of each group of beams; The bending stress of each group of beams is obtained accordingly. and shear stress : , The elastic modulus of the material; , This is the shear modulus of the material.

7. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 1, characterized in that, When the load is a winding Torque of the shaft The stress and strain distributions of beam AB are then analyzed using the following steps: Calculate the position of beam AB at any location. Torsional coefficient at the section : ,in, The shape factor, for The width of the cross section at that location, The height of the elastic beam; Based on the cross-sectional torsional coefficient Calculate the position of beam AB at any location. shear force at the point : ; Combined with the aforementioned cross-sectional torsional coefficient and shear force The longitudinal strain of beam AB was obtained. and positive strain : , For any position of beam AB The corresponding beam height; , The Poisson's ratio represents the material of the beam; Correspondingly, AB beam The normal stress in the axial direction is : , The elastic modulus of the material; AB beam The normal stress in the axial direction is : .

8. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 7, characterized in that, Based on the structural relationship between beams AB and EF, the stress and strain distributions of beam EF are analyzed through the following steps: Establish the force equilibrium equations for beams AB, CD, and EF: ,in, It is the moment borne by beam AB. It is the counter-constraint force at end C of beam CD. The radius of the central platform; Based on the geometric relationships between beams AB, CD, and EF, establish the force relationships: , For the forces acting on beam AB, The forces at ends C and E of beams CD and EF are respectively. For combined efforts; By combining the aforementioned force equilibrium equations, the solution is obtained. : ; Therefore, the strains of both beam CD and beam EF are : , yes The cross-sectional area at that location; The stresses of both beam CD and beam EF are : .

9. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 1, characterized in that, When the load is a winding Torque of the shaft At that time, beams AB, CD, and EF are subjected to the same forces. Taking beam AB as the analysis object, the stress and strain distribution of beam AB are obtained through the following steps: Based on the principle of torque balance, determine the counter-torque of the outer single beam of beam AB. And at any position along the axial direction of beam AB Bending moment at section ; The bending strain of beam AB is calculated using the following formula. and shear strain : ， For any position of beam AB The corresponding beam height, The elastic modulus of the material. Let G be the moment of inertia of beam AB about the z-axis, and G be the shear modulus of the material. yes The cross-sectional area at that point, This is the shear correction factor; Based on the bending strain and shear strain The bending normal stress was calculated separately. and shear stress : ， 。 10. The decoupling method for an integrated six-dimensional force sensor for combine harvesters according to claim 1, characterized in that, The construction process of the six-dimensional output model includes: Using the processed electrical signal as input data, variable selection is performed on the input data to identify feature variables that are highly correlated with load prediction and use them as input features to form a training sample set. The preset six-dimensional loads corresponding to the input features are used as output data to form the output matrix. ; For the training sample set and output matrix Standardize them separately to obtain standardized training sample sets. and standardized output matrix , Based on the support vector regression model, with a standardized training sample set and standardized output matrix Based on this, a load prediction model is built, and the kernel function of the load prediction model is created. The kernel function The expression is as follows: ,in, It is the first and the One input sample, This is the kernel function width parameter; A grid search method is used to perform a search on the kernel function width parameter. Optimize the kernel width parameter until the performance of the load prediction model is optimal. ; The mapping relationship between the processed electrical signal and the load borne by the integrated six-dimensional force sensor is determined, and the six-dimensional output model of the integrated six-dimensional force sensor is obtained.

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