Decoupling method for integrated six-axis force sensor for combine harvester

Abstract

The application 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" type three-beam radial symmetric structure, highly integrates a belt wheel function and a six-dimensional force detection function, establishes an elastic body structure simplified mechanics model, establishes a semi-analytical method model, analyzes and obtains strain distribution laws of X, Y and Z under single-axis load, and obtains a sensor geometric structure and a strain gauge measurement position meeting design requirements according to the strain distribution laws; a multi-output least square support vector regression machine is adopted, hyperparameters are optimized through a grid search, a high-precision mapping model of an electric signal to six-dimensional load is constructed, the decoupling precision is greatly improved, a whole-process innovation from structure to stress analysis and then to decoupling is realized, and the method is especially suitable for agricultural mechanical scenes such as a combine harvester and the like which are space-limited and have complex load.

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 and high humidity), the installation of external sensors is often limited by space and is easily disturbed by the outside world, resulting in a decrease in measurement accuracy.

[0003] Currently, six-dimensional force sensors are widely used in industries such as robots, automobiles, medical treatment and aerospace, and can directly measure the transformation of forces in XYZ three directions in space and the size of torque, with the advantages of small size, compact structure and low cost, but their application in the field of agricultural machinery still has the following problems:

[0004] 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.

[0005] 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.

[0006] 3. The strain analysis model of traditional sensors may not accurately reflect the actual load distribution of the harvester belt wheel. SUMMARY

[0007] 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.

[0008] The application adopts the following technical scheme: a decoupling method of an integrated six-dimensional force sensor for a combine harvester, comprising the following steps:

[0009] An integrated six-dimensional force sensor with a belt wheel and a six-dimensional sensor is designed, the integrated six-dimensional force sensor comprises: a center table, a plurality of groups of elastic beams fixed on the outer side of the center table in the radial direction; physical parameter information of the integrated six-dimensional force sensor is obtained, and a sensor mechanics model is simplified;

[0010] The 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;

[0011] 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.

[0012] 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.

[0013] 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.

[0014] In a further embodiment, the process of obtaining the sensor's mechanical model is as follows:

[0015] 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, and the y-axis is at... 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:

[0016] ,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;

[0017] Establish a local coordinate system based on physical parameter information. The sensor's mechanical model is expressed as follows:

[0018] ;

[0019] 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;

[0020] Based on the spatial transformation relationship, a six-dimensional load vector in the global rectangular coordinate system is obtained through a six-dimensional load vector in the local coordinate system .

[0021] In further embodiments, the elastic beams are three groups, evenly distributed along the circumference to form a Y-shaped structure.

[0022] One of the elastic beams in the Y-shaped structure is defined as AB beam, and the elastic beams on both sides of the AB beam are respectively CD beam and EF beam.

[0023] The multi-directional load includes: axial force , axial force , torque around axis , and torque around axial direction .

[0024] In further embodiments, when the load is axial force , the stress distribution and strain distribution of the AB beam are analyzed by the following steps:

[0025] The force deflection series form and the rotation angle series form of the AB beam are established, which respectively contain the deflection series coefficient and the rotation angle series coefficient to be solved; ;

[0026] The force deflection series form and the rotation angle series form are substituted into the force geometry relationship of the AB beam, and the weighted residual method is used to form an algebraic equation set, which is simplified into a matrix form , wherein H is the coefficient matrix, C is the unknown vector containing the deflection series coefficient and the rotation angle series coefficient , and F is the load vector.

[0027] The deflection series coefficient and the rotation angle series coefficient are solved by the Gaussian elimination method, and the bending stress and the shear stress of the AB beam under the force are calculated:

[0028] , ​​; wherein is the cross-sectional width of the elastic beam at the point , is the height of the elastic beam, and L is the length of the elastic beam, is the cross-sectional area of the elastic beam at the point , is the shear strain of the elastic beam at the point , is the shear correction factor;

[0029] correspondingly, the bending strain and the shear strain of the AB beam under the force are obtained as follows:

[0030] , wherein, is the elastic modulus of the material, is the shear modulus of the material.

[0031] In further embodiments, based on the structural relationship between the AB beam and the EF beam, the strain distribution of the EF beam is analyzed by the following steps:

[0032] Based on the AB beam, the force balance equation of the EF beam is established as follows: wherein, and are the forces at the E end of the EF beam and the A end of the AB beam;

[0033] At the same time, the initial disturbance relationship between the AB beam and the EF beam is established as follows: , is the deflection of the AB beam under the force, is the equation coefficient;

[0034] The constraint force at the E end of the EF beam is orthogonally decomposed into an axial force component and a 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;

[0035] The strain of the EF beam is obtained by the following formula: , is the elastic modulus of the material, is the cross-sectional area of the elastic beam at the point .

[0036] In further embodiments, when the load is an 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:

[0037] The force balance relationship of the AB beam, the CD beam and the EF beam is established: ; wherein, , , are the forces borne by the A end, the C end and the E end of the AB beam, the CD beam and the EF beam respectively;

[0038] Based on the force balance relationship, the bending strain and the shear strain of each group of beams are solved respectively, i.e. the strain distribution of each group of beams;

[0039] Correspondingly, the bending stress and the shear stress of each group of beams are obtained: , is the elastic modulus of the material;

[0040] , is the shear modulus of the material.

[0041] 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:

[0042] The cross-section torsion coefficient of the AB beam at any position is calculated: , wherein, is the shape coefficient, is the cross-sectional width at , and is the height of the elastic beam;

[0043] The shear force of the AB beam at any position is calculated based on the cross-section torsion coefficient : ; and

[0044] The longitudinal strain and the positive strain of the AB beam are obtained in combination with the cross-section torsion coefficient and the shear force :

[0045] , is the corresponding beam height at any position of the AB beam;

[0046] , represents the material Poisson's ratio of the beam;

[0047] corresponding to the AB beam The positive stress in the axial direction is : , is the material elastic modulus;

[0048] AB beam The positive stress in the axial direction is : .

[0049] In further embodiments, based on the structural relationship of the AB beam and the EF beam, the stress distribution and strain distribution of the EF beam are analyzed by the following steps:

[0050] The force balance equation between the AB beam, the CD beam and the EF beam is established: wherein, is the moment of force 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;

[0051] According to the geometric relationship between the AB beam, the CD beam and the EF beam, the force relationship is established: , is the force borne by the AB beam, are the forces borne by the C end and the E end of the CD beam and the EF beam respectively, is the resultant force;

[0052] Combined with the force balance equation, it is solved that : ;

[0053] Therefore, the strain of the CD beam and the EF beam is : , is the cross-sectional area at ;

[0054] The stress of the CD beam and the EF beam is : .

[0055] In further embodiments, when the load is the moment of force around the axis , the forces borne by the AB beam, the CD beam and the EF beam are the same, and the AB beam is taken as the analysis object, and the stress distribution and strain distribution of the AB beam are analyzed by the following steps:

[0056] Based on the moment balance principle, the counter-moment of the outer single of the AB beam is determined , and the bending moment of the cross section of the AB beam at any position of the axial direction of the AB beam ; ;

[0057] The bending strain and the shear strain of the AB beam are calculated by using the following formulas :

[0058] ,

[0059] is the corresponding beam height at any position of the AB beam , is the elastic modulus of the material, is the 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 the position , is a shear correction coefficient;

[0060] The bending normal stress and the shear stress are calculated based on the bending strain and the shear strain respectively :

[0061] , .

[0062] In further embodiments, the construction process of the six-dimensional output model comprises:

[0063] The processed electrical signal is taken as input data, variable screening is performed on the input data, feature variables with strong correlation with load prediction are selected and taken as input features to form a training sample set ; the preset six-dimensional load corresponding to the input features is taken as output data to form an output matrix ;

[0064] The training sample set and the output matrix are standardized respectively to obtain a standardized training sample set and a standardized output matrix ,

[0065] Based on the support vector regression model, the standardized training sample set and the standardized output matrix are taken as the basis to build a load prediction model, and a kernel function of the load prediction model is created , and the expression form of the kernel function is as follows:

[0066] ​​wherein, is the and the input sample, is a kernel function width parameter;

[0067] A grid search method is used to optimize the kernel function width parameter until the kernel function width parameter that optimizes the performance of the load prediction model is obtained.

[0068] A mapping relationship between the processed electrical signal and the load borne by the integrated six-dimensional force sensor is determined to obtain a six-dimensional output model of the integrated six-dimensional force sensor.

[0069] The beneficial effects of the present application are as follows: the present application designs the belt wheel and the six-dimensional sensor into an integrated structure, which greatly reduces the connection gap and assembly error of parts compared with the traditional "sensor, belt wheel" split type scheme, effectively avoiding the load measurement deviation caused by vibration and impact during the operation of the combine harvester (such as grain harvesting and straw crushing). At the same time, the three groups of elastic beams (Y-shaped structure) uniformly distributed along the radial direction of the center platform can balance the multi-directional load. For example: axial force , axial force , torque around axle , and torque around axial direction , which adapt to the complex stress environment of the belt wheel of the combine harvester and improve the overall structural stability and service life of the sensor.

[0070] The present application establishes the load conversion relationship between the local coordinate system and the overall rectangular coordinate system , constructs a mechanical model that fits the actual structure of the sensor, avoids the theoretical error caused by the simplified model, and provides accurate mechanical basis for subsequent load decoupling.

[0071] The present application verifies and determines the best 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.

[0072] The application constructs a six-dimensional output model by denoising the collected strain gauge output signal, combining the standardized training sample and the support vector regression model (SVR), and optimizing the kernel function parameters through grid search 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), this model can effectively handle the coupling effect between loads, and even in the scene of dynamic operation of the combine harvester (such as load mutation and multi-load superposition), it can quickly output accurate six-dimensional load data, providing 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

[0073] Figure 1 is a flowchart of the decoupling method of the integrated six-dimensional force sensor for the combine harvester.

[0074] Figure 2 is a structural schematic diagram of the integrated six-dimensional force sensor.

[0075] Figure 3 is a relationship diagram between the local coordinate system and the overall orthogonal coordinate system .

[0076] Figure 4 is a sensor mechanics model diagram.

[0077] Figure 5 is a three-view diagram of beam AB.

[0078] Figure 6 is a force diagram of an elastic beam.

[0079] Figure 7 is an MLS-SVR intuitive principle diagram.

[0080] Figure 8 is a K-fold cross-validation principle diagram.

[0081] Figure 2 Each label in is: outer shell 1, elastic beam 2, center table 3, mounting groove 4, double-belt groove structure 101. DETAILED DESCRIPTION

[0082] The application will be further described below in conjunction with the drawings and examples of the specification.

[0083] Example 1

[0084] As shown in Figure 1 , the decoupling method of the integrated six-dimensional force sensor for the combine harvester includes the following steps:

[0085] The integrated six-dimensional force sensor with a pulley and a six-dimensional sensor integrated includes a center table, a plurality of sets of elastic beams fixed on the outer side of the center table in the radial direction, and a physical parameter information acquisition module.

[0086] The stress distribution or strain distribution of each set of elastic beams is analyzed by applying a multi-directional load to the integrated six-dimensional force sensor.

[0087] Based on the stress distribution or strain distribution of each set of elastic beams, the installation scheme of a plurality of stress sheets is verified to determine the optimal installation position of each set of elastic beams, and the corresponding stress sheet is installed.

[0088] A preset six-dimensional load is applied to the integrated six-dimensional force sensor, and the output signals of each set of stress sheets are collected in real time, and the output signals are denoised to obtain processed electrical signals.

[0089] 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.

[0090] Further, in combination with Figures 2 to 5 The integrated six-dimensional force sensor according to the embodiment has a specific structure that the elastic beams are three sets and are uniformly distributed along the circumference to form a Y-shaped structure.

[0091] One elastic beam in the Y-shaped structure is defined as an AB beam, and the elastic beams on both sides of the AB beam are respectively a CD beam and an EF beam; and a mounting groove is formed at a specified position of each beam, and the mounting groove is used for corresponding installation of a stress sheet. The center table, the elastic beam and the outer shell in the embodiment are processed by an alloy material; and the mounting groove is obtained by quenching treatment.

[0092] As shown in Figure 2 The integrated six-dimensional force sensor includes an outer shell 1, an elastic beam 2 and a center table 3. The main structure of the outer shell 1 is a circular ring, and a double-belt groove structure 101 is arranged. The main structure of the elastic beam 2 is a trapezoid, and a square stress mounting groove 4 is arranged in the middle. The main structure of the center table 3 is a circular ring.

[0093] The six-dimensional force sensor is installed at a pulley in a drive device outside a harvester, directly replaces the original pulley and is used, cooperates with a hole in the center table with a diameter of 50 mm, and the outer shell has a pulley groove with a diameter of 300 mm for belt installation. After installation, the sensor receives signals by using a wireless device, meets the use of the pulley of the harvester, and is also used as a sensor. The strain gauges in the square strain gauge groove on the elastic beam form a strain gauge group, which is used to detect the load borne by the sensor and output an electrical signal.

[0094] 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 .

[0095] 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:

[0096] 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:

[0097] ,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;

[0098] Establish a local coordinate system based on physical parameter information. The sensor's mechanical model is expressed as follows:

[0099] ;

[0100] 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;

[0101] 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.

[0102] Combination Figure 3 Taking a six-axis load as an example, global rectangular coordinate system The six-dimensional load vector below, ,in, , and respectively along Force on the axis, , and They are respectively around Torque on the shaft;

[0103] Local coordinate system The six-dimensional load vector below, , , and respectively along Force on the axis, , and They are respectively around Torque on the shaft;

[0104] This is the load transformation matrix. ;in, for axis, The included angle between the axes, in this embodiment .

[0105] By adopting the above technical solution, the local model is used to ensure the accuracy of stress and strain analysis of a single elastic beam, while the load transformation matrix integrates the local forces of multiple beams into a total six-dimensional load. The combination of the two provides a unified mechanical benchmark for the subsequent "strain gauge installation position verification" and "six-dimensional output model construction", avoiding decoupling errors caused by the ambiguity of the correspondence between local and overall loads, and laying a key theoretical foundation for the sensor to finally achieve accurate measurement of six-dimensional load.

[0106] 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 section of the beam is selected for slotting and pasting the strain sheet to obtain relatively stable and reliable strain data.

[0107] For example, the multi-directional load of the embodiment includes: Figure 6 axial force , axial force , torque around axis , and torque around axial direction .

[0108] Further, when the load is axial force , the stress distribution and strain distribution of the AB beam are analyzed by the following steps:

[0109] establishing the force deflection form and the rotation angle form of the AB beam, wherein the force deflection form and the rotation angle form respectively contain the deflection series coefficient and the rotation angle series coefficient to be solved.

[0110] 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, .

[0111] wherein the deflection series base function and the rotation angle series base function are respectively represented as: , .

[0112] the force deflection ​Series form and rotation Substituting the numerical form into the geometric force relationships of beam AB,

[0113] 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.

[0114] 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.

[0115] 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 :

[0116] , ;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;

[0117] Correspondingly, the stress on beam AB is obtained. Bending strain and shear strain :

[0118] , ,in, The elastic modulus of the material. This is the shear modulus of the material.

[0119] 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.

[0120] Based on the structural relationship between beams AB and EF, the stress distribution of beam EF is obtained through the following steps:

[0121] 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;

[0122] 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;

[0123] 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 ;

[0124] The strain of beam EF is obtained using the following formula. : , The elastic modulus of the material. elastic beam The cross-sectional area at that point.

[0125] 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:

[0126] 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.

[0127] 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;

[0128] The bending stress of each group of beams is obtained accordingly. and shear stress : , The elastic modulus of the material;

[0129] , This is the shear modulus of the material.

[0130] 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:

[0131] 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;

[0132] Based on the cross-sectional torsional coefficient Calculate the position of beam AB at any location. shear force at the point : ;

[0133] 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;

[0134] , The Poisson's ratio represents the material of the beam;

[0135] Correspondingly, AB beam The normal stress in the axial direction is : , The elastic modulus of the material;

[0136] AB beam The normal stress in the axial direction is : .

[0137] Based on this, for the mechanical energy analysis of the mutually symmetrical beams CD and EF, the stress distribution and strain distribution of beam EF are obtained through the following steps:

[0138] 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;

[0139] Based on the geometric relationships between beams AB, CD, and EF, establish the force relationships: , is the force of the AB beam, are the forces of the C end and E end of the CD beam and EF beam respectively, is the resultant force;

[0140] According to the force balance equation, the following is obtained: ;

[0141] The strain of the CD beam and EF beam is: , is the cross-sectional area at the position ;

[0142] The stress of the CD beam and EF beam is: .

[0143] In another embodiment, when the load is a torque around the axis, the forces of the AB beam, CD beam and EF beam are the same. Taking the beam AB as the analysis object, the stress distribution and strain distribution of the AB beam are analyzed by the following steps: Based on the torque balance principle, the counter torque

[0144] 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;

[0145] The bending strain and shear strain of the AB beam are calculated by the following formula:

[0146] ,

[0147] 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 the position , is the shear correction coefficient;

[0148] The bending normal stress and shear stress are calculated respectively based on the bending strain and shear strain :

[0149] ,​​​​ .

[0150] Finally, the embodiment also discloses a construction process of the six-dimensional output model, which comprises:

[0151] Taking the processed electrical signal as input data, variable screening is performed on the input data, and a characteristic variable with strong correlation with load prediction is selected as an input feature to form a training sample set ; a preset six-dimensional load corresponding to the input feature is taken as output data to form an output matrix ;

[0152] The training sample set and the output matrix are standardized respectively to obtain a standardized training sample set and a standardized output matrix ; the standardization processing in the embodiment can be a Z-Score standardization method.

[0153] Based on the support vector regression model, the standardized training sample set Figure 7 and the standardized output matrix are used as a basis to build a load prediction model, a kernel function of the load prediction model is created , and an expression form of the kernel function is as follows:

[0154] wherein, x i is an i th input sample, x j is a j th input sample, is a kernel function width parameter; A grid search method is used to optimize the kernel function width parameter until a kernel function width parameter

[0155] making the load prediction model optimal is obtained; K-fold cross validation is used to evaluate the average performance index of the model. As shown in FIG. 6, 4-fold cross validation is used in the embodiment to find a hyperparameter making the mean square error (MSE) minimum and the determination coefficient (R 2 ) maximum. The mapping relationship between the processed electrical signal and the load borne by the integrated six-dimensional force sensor is determined to obtain a six-dimensional output model of the integrated six-dimensional force sensor, i.e., output borne load values Figure 8 , ,

[0156] , , , , , , , and decoupling is completed.​

[0157] The corresponding relationship between the electric 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, and the decoupling result is shown in Table 1.

[0158] Table 1

[0159]

[0160] Based on the decoupling result of the experimental measurement data by the multi-output least square support vector regression, the effect is excellent, the coupling problem between the signals of the six-dimensional force sensor can be well solved, and the measurement precision is improved.

[0161] 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 and do not limit the specific implementation 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 the persons 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. Decoupling method for a combined harvester-oriented integrated six- dimensional force sensor, characterized by, The method comprises the following steps: An integrated six-dimensional force sensor is designed, which integrates a pulley and a six-dimensional sensor, and comprises a center platform, a plurality of groups of elastic beams fixed on the outer side of the center platform in a radial direction, and a physical parameter information acquisition module for acquiring physical parameter information of the integrated six-dimensional force sensor and simplifying a sensor mechanical model; A stress distribution or a strain distribution of each group of elastic beams is analyzed by separately applying multidirectional loads to the integrated six-dimensional force sensor; Based on the stress distribution or the strain distribution of each group of elastic beams, an installation scheme of a plurality of stress sheets is verified to determine an optimal installation position of each group of elastic beams, and a corresponding stress sheet is installed; A preset six-dimensional load is applied to the integrated six-dimensional force sensor, and output signals of each group of stress sheets are collected in real time, and 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, actual six-dimensional loads borne by the integrated six-dimensional force sensor are output, and decoupling is completed; The sensor mechanical model is obtained by the following process: Establish a local coordinate system : the center of the center platform as the origin, the axis along the AB beam axis outward, the axis in the plane is perpendicular to the axis is angle, the axis is perpendicular to the plane; the load satisfies the following spatial conversion relationship between the global rectangular coordinate system and the local coordinate system ​ ,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; Based on the physical parameter information, a local coordinate system is established The sensor mechanics model under the local coordinate system is expressed as follows: ； where 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 and outer end widths of the elastic beam, is the height of the elastic beam; Based on the spatial transformation relationship, a six-dimensional load vector under the global rectangular coordinate system is obtained through a six-dimensional load vector under the local coordinate system . .

2. The decoupling method of a combine-harvester-oriented integrated six-axis force sensor according to claim 1, characterized in that, The elastic beams are three groups and are uniformly distributed along the circumference to form a Y-shaped structure; One elastic beam in the Y-shaped structure is defined as an AB beam, and elastic beams located on both sides of the AB beam are CD and EF beams; The multi-directional load includes: a force in the axial direction , a force in the axial direction , a moment about the axis , and a moment about the axial direction .

3. The decoupling method of a combine-harvester-oriented integrated six-axis force sensor according to claim 2, characterized in that, When the load is axial force The stress distribution and strain distribution of the AB beam are analyzed by the following steps: Establishing the deflection of an AB beam under load The number of terms and the angle of rotation The number of terms and the angle of rotation The number of terms and the angle of rotation The number of terms and the angle of rotation The number of terms and the angle of rotation ; The deflection under load The deflection under load The deflection under load Where H is the coefficient matrix, C is the unknown vector containing the deflection series coefficients And the rotation series coefficients And 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 : , ; wherein, is the cross-sectional width at the point, is the height of the elastic beam, L is the length of the elastic beam, the cross-sectional area of the elastic beam at the point, is the shear strain of the elastic beam at the point, is the shear correction factor;​​ Corresponding bending strain and shear strain of AB beam at force :​​ , wherein, is the material elastic modulus, is the material shear modulus.

4. The decoupling method of a combine-harvester-oriented integrated six-axis force sensor according to claim 3, characterized in that, Based on the structural relationship between 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 stress equilibrium equation of the EF beam is established: wherein, and are the stresses at the E end of the EF beam and the A end of the AB beam. At the same time, the initial deflection relationship of AB beam and EF beam is established: , is the stress deflection of AB beam, is the equation coefficient; Orthogonally decomposing the constraint force on the E end of the EF beam into an axial force component and a tangential force component , and solving the equation coefficients based on the geometric relationship balance equation of the EF beam and a tangential force component ; The strain of the EF beam is obtained using the following equation : , E is the modulus of elasticity of the material, A is the cross-sectional area of the elastic beam at .

5. The decoupling method of a combine-harvester-oriented integrated six-axis force sensor according to claim 2, characterized in that, 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 the 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, , , respectively, A, C, E of the AB beam, the CD beam and the EF beam are the forces suffered by the end. solving the bending strain of each group of beams based on the force balance relationship and shear strain i.e. the strain distribution of each group of beams; corresponding to the bending stress of each group of beams and shear stress : , E is the modulus of elasticity of the material; , G is the shear modulus of the material.

6. The decoupling method of a combine-harvester-oriented integrated six-axis force sensor according to claim 2, characterized in that, When the load is a moment about the axis of the beam The stress distribution and strain distribution of the AB beam are analyzed by the following steps: The cross-sectional torsion coefficient at any position of the AB beam : : wherein, is a shape coefficient, is is the cross-sectional width at the position, is the height of the elastic beam; Based on the torsion coefficient of cross section Calculating shear forces at any location of an ab beam : : ; in combination with the cross-sectional torsion coefficient and shear forces to obtain the longitudinal strain of the AB beam and the positive strain : , H(x) = H0+ (H1- H0) x / L H(x) = H0+ (H1- H0) x / L , the material Poisson's ratio of the beam; Correspondingly, AB beam The positive stress in the axial direction is : , E is the modulus of elasticity of the material; AB beam The positive stress in the axial direction is : .

7. The decoupling method of a combine-harvester-oriented integrated six-axis force sensor according to claim 6, characterized in that, Based on the structural relationship between the AB beam and the EF beam, the stress distribution and the strain distribution of the EF beam are analyzed by the following steps: The force balance equations between the AB beam, CD beam and EF beam are established: wherein, is the moment of force 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, a 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; In combination with the force balance equation, the following is obtained : ; Then, the strain of the CD beam and the EF beam are both : , is the cross-sectional area at the location The stress of the CD beam and the EF beam are both : .

8. The method of decoupling a combined harvester-oriented integrated six-axis force sensor of claim 2, wherein, 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 at end B of beam AB. And at any position along the axial direction of beam AB Bending moment at section ; The bending strain of the AB beam is calculated using the following equation and the shear strain : ， for any position of the AB beam corresponding to the beam height at the position, is the modulus of elasticity of the material, is the moment of inertia of the cross-section of the AB beam about the z-axis, and G is the shear modulus of the material, is is the cross-sectional area at the position, is the shear correction factor; based on the bending strain and the shear strain the bending normal stress and the shear stress are calculated respectively ， 。 9. The method of decoupling a combine-harvester-oriented integrated six-axis force sensor according to claim 1, characterized in that, The construction process of the six-dimensional output model comprises: Taking the processed electric signal as input data, performing variable screening on the input data, selecting characteristic variables with strong correlation with load prediction as input characteristics, and constituting a training sample set ; taking the preset six-dimensional load corresponding to the input characteristics as output data, and constituting an output matrix ; The training sample set is standardized, and a standardized training sample set is obtained. The output matrix is standardized, and a standardized output matrix is obtained. The training sample set is standardized, and a standardized training sample set is obtained. The output matrix is standardized, and a standardized output matrix is obtained. The training sample set is standardized, and a standardized training sample set is obtained. The output matrix is standardized, and a standardized output matrix is obtained. The training Based on the support vector regression model, the standardized training sample set and the standardized output matrix are used as the basis to build the load prediction model, and the kernel function of the load prediction model is created , and the expression form of the kernel function is as follows: wherein, is the and the input sample, is a kernel function width parameter; The kernel function width parameter is optimized by using a grid search method until a kernel function width parameter is obtained, which makes the performance of the load prediction model optimal. The kernel function width parameter is optimized by using a grid search method until a kernel function width parameter is obtained, which makes the performance of the load prediction model optimal. The kernel function width parameter is optimized by using a grid search method until a kernel function width parameter is A mapping relationship between the processed electrical signals and the loads borne by the integrated six-dimensional force sensor is determined, and a six-dimensional output model of the integrated six-dimensional force sensor is obtained.

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