Force measurement system, force measurement system structure optimization method and device, and force measurement branch structure optimization method and device

Abstract

The invention belongs to the technical field of force measurement system optimization, and particularly relates to a force measurement system, a force measurement system structure optimization method and device, and a force measurement branch structure optimization method and device. According to the whole scheme, the main structure optimization of the force measurement system is divided into three parts, namely the structure parameter optimization of the force measurement branch, the structure parameter optimization of the non-branch structure and the structure parameter fine adjustment of the whole force measurement system, and each part is subjected to quantitative design, so that the design efficiency and accuracy of the force measurement system are improved. Wherein in the quantitative design process of each part, an elastic resistance error is used as a forward design index, the elastic resistance error is one of main components in coupling errors, structural parameters related to the elastic resistance error are relatively comprehensive, and the influence of axial rigidity and cornering rigidity of force measurement on structural performance is considered; the method has very high correlation with the structural parameters of the force measuring system, and can ensure the accuracy of structural analysis and design.

Description

Technical Field

[0001] The present invention belongs to the technical field of force measurement system optimization, and specifically relates to a force measurement system and a method and device for optimizing the structure of a force measurement system, and a method and device for optimizing the structure of a force measurement branch. Background Art

[0002] At present, with the advancement of aerospace vector thrust technology, as well as the rapid development of industrial automation, precision manufacturing and robotics, the demand for high-precision vector force measurement systems is growing. In the field of aerospace, related equipment (called vector force measurement system, test bench, six-component balance, box balance, force measurement system, etc.) is the key equipment for measuring engine thrust or model load in the aerospace field. With the improvement of the requirements for vector thrust technology of the new generation of fighters and the development of wind tunnel load measurement technology, the demand for high-precision and heavy-load vector thrust measurement systems is becoming more and more urgent. In the fields of robotics, most applications are small vector force measurement systems, which are generally called force sensors, six-dimensional force sensors, six-axis force / torque sensors, etc., and are one of the key sensors in the field of robotics. At present, there is a huge market demand for high-precision small vector force measurement systems, so it is of great significance to explore the high-precision design technology of vector force measurement systems.

[0003] The current theoretical research on the structural design of force measurement systems mainly focuses on sensitivity analysis and isotropic design. Its theoretical basis is mostly based on two basic assumptions: first, it is assumed that the force measurement branch is only subjected to axial loads; second, the non-branch structures such as the movable frame and the support are idealized and regarded as rigid bodies without deformation. Under this simplified theoretical assumption, the design work focuses on optimizing the layout and axial stiffness of the force measurement system branches to achieve enhanced structural sensitivity and isotropic characteristics. This process derives many design conclusions with practical value. However, this method ignores the influence of key structural characteristics such as the lateral stiffness of the force measurement branch and the stiffness of the non-branch structure of the non-force measurement branch in the system, which restricts the structural design of the force measurement system to a certain extent.

[0004] In the current structural design practice of force measurement systems, finite element models are widely used as the main tool. The typical design process includes the designer preliminarily drafting the basic structural framework, and then using finite element analysis technology to carry out detailed design of the core component - the force measurement branch, and conducting strength and frequency evaluation of important non-branch structures such as the dynamic frame and the support. This method can basically meet the actual needs. However, this design method is particularly dependent on the designer's rich professional experience, and fails to fully optimize the structural parameters from the perspective of the overall performance of the system. Another design method involves using finite element analysis software to create a relatively accurate simulation model, and by continuously adjusting the geometric features and layout parameters of the force measurement branch, a comprehensive parameter iteration optimization is performed until the key performance indicators such as the system stiffness meet the standards. This structural design method based on parameter optimization usually achieves better results. However, this process is highly dependent on huge computing power resources and requires designers to perform complex and time-consuming analysis workflows.

[0005] As an important structure in the force measurement system, the structural optimization design of the force measurement branch is of vital importance. In general, coupling error is often used as one of the key indicators of the force measurement system to reflect the measurement performance of the force measurement branch in the force measurement system. However, there are many sources of coupling error, which is affected by many factors. In addition to system structural factors, there are coupling errors caused by processing and assembly errors, coupling errors caused by material properties, electrical coupling errors, and coupling errors between data acquisition channels. At the same time, the sensitivity of the diagonal elements and non-diagonal elements in the coupling error to various interferences is unclear. This multi-factor and vague sensitivity situation makes it inappropriate to use it directly as a structural design indicator, resulting in poor structural forward design results and restricting the further development of vector force measurement technology. Summary of the invention

[0006] The purpose of the present invention is to provide a force measuring system and a force measuring system structure optimization method and device, a force measuring branch structure optimization method and device, so as to solve the problem of poor structural forward design effect caused by using coupling error as an indicator.

[0007] In order to solve the above technical problems, the present invention provides a method for optimizing the force measurement branch structure in a force measurement system, the method comprising:

[0008] 1) Constructing a simulation model of the force measurement branch according to the initial structural parameters of the force measurement branch;

[0009] 2) Using the latest simulation model of the force measurement branch to determine whether the force measurement branch index has converged: if it has converged, the structural parameters of the force measurement branch are optimal at this time; otherwise, the structural parameters of the force measurement branch are adjusted to reduce the force measurement branch index and the simulation model of the force measurement branch is re-determined, and then step 2) is re-executed to iterate until convergence;

[0010] The force measuring branch index is the elastic resistance error coefficient of ignoring deformation factors in three directions; wherein the elastic resistance error coefficient of ignoring deformation factors in a certain direction is the sum of the elastic resistance error coefficients of ignoring deformation factors generated by the other two force measuring branches for the force measurement in the certain direction, and the elastic resistance error coefficient of ignoring deformation factors generated by the other force measuring branches for the force measurement in the certain direction is the product of the ratio of the number of the other force measuring branches in the one direction to the force measuring branches in the one direction, the ratio of the axial stiffness of the other force measuring branches in the one direction to the force measuring branches in the one direction, and the ratio of the lateral stiffness of the other force measuring branches in the one direction to the axial stiffness of the other force measuring branches in the one direction.

[0011] Furthermore, the simulation model is a finite element simulation model.

[0012] In order to solve the above technical problems, the present invention further provides a computer device, including a processor, wherein the processor executes a computer program to implement the steps of the force measurement branch structure optimization method in the force measurement system introduced above.

[0013] The present invention is an improved invention creation. The force measuring branch structure optimization method and computer device in the force measuring system of the present invention take into account that the elastic resistance error is one of the main components of the coupling error, and the structural parameters of the elastic resistance error design are relatively comprehensive, and the influence of the axial stiffness and lateral stiffness of the force measurement on the structural performance is considered, and it has a high correlation with the design parameters of the force measuring system. The present invention uses the elastic resistance error as an evaluation index of the structural design to improve the accuracy of the structural design. Moreover, in the process of optimizing the force measuring branch structure in the force measuring system, the elastic resistance error coefficient that ignores the deformation factor is adopted, which can improve the efficiency of the subsequent structural design and optimization of the entire force measuring system. In addition, the present invention is a general structural design method that combines the elastic resistance error and simulation, giving full play to the advantages of theoretical methods in analyzing the relationship between structural performance and design parameters in the deformation and local load accurate calculation.

[0014] In order to solve the above technical problems, the present invention also provides a method for optimizing the structure of a force measurement system, the method comprising:

[0015] 1) Constructing a simulation model of the force measuring branch in the force measuring system according to the initial structural parameters of the force measuring branch;

[0016] 2) Using the latest simulation model of the force measurement branch to determine whether the force measurement branch index has converged: if not, adjusting the structural parameters of the force measurement branch to reduce the force measurement branch index and re-determining the simulation model of the force measurement branch, and then re-execute step 2) to iterate until convergence; if converged, execute step 3);

[0017] The force measurement branch index is the elastic resistance error coefficient of ignoring deformation factors in three directions; wherein, the elastic resistance error coefficient of ignoring deformation factors in a certain direction is the sum of the elastic resistance error coefficients of ignoring deformation factors generated by the remaining two force measurement branches for the force measurement in the certain direction, and the elastic resistance error coefficient of ignoring deformation factors generated by the remaining one-way force measurement branches for the force measurement in the certain direction is the product of the ratio of the number of the remaining one-way force measurement branches to the force measurement branches in the certain direction, the ratio of the axial stiffness of the remaining one-way force measurement branches to the force measurement branches in the certain direction, and the ratio of the lateral stiffness of the remaining one-way force measurement branches to the axial stiffness of the remaining one-way force measurement branches;

[0018] 3) constructing a simulation model of the force measurement system according to the initial structural parameters of the non-branch structure and the structural parameters of the force measurement branch finally determined in step 2); wherein the non-branch structure is the structure in the force measurement system other than the force measurement branch;

[0019] 4) Use the latest simulation model of the force measurement system to determine whether the non-branch structure indicators meet the index requirements: if so, the structural parameters of the non-branch structure are optimal at this time; if not, adjust the structural parameters of the non-branch structure and re-determine the simulation model of the force measurement system, and then re-execute step 4) to iterate until the non-branch structure indicators meet the index requirements.

[0020] Furthermore, in step 4), the non-branching structure index is the non-branching structure evaluation coefficient in each direction, and the non-branching structure evaluation coefficient in a certain direction is the difference between the elastic resistance error coefficient in the certain direction considering the deformation factor and the elastic resistance error coefficient in the certain direction ignoring the deformation factor;

[0021] The elastic resistance error coefficient considering deformation factor in a certain direction is the sum of the elastic resistance error coefficients considering deformation factor generated by the force measurement branches in the other two directions for the force measurement in the certain direction, and the elastic resistance error coefficient considering deformation factor is:

[0022]

[0023] Where, T fi,ji It represents the elastic resistance error coefficient of the i-direction force measurement branch on the y-direction force measurement; n i Indicates the number of force measurement branches in direction i; n j Indicates the number of force measurement branches in the j direction; K fi,ui It represents the displacement stiffness along the i-direction caused by the force component of the i-direction force-measuring branch in the global coordinate system, which is called the axial stiffness of the i-direction force-measuring branch; K fj,uj K represents the displacement stiffness along the j direction caused by the force component of the j-direction force-measuring branch in the global coordinate system, which is called the axial stiffness of the j-direction force-measuring branch; fi,uj K represents the displacement stiffness along the i direction caused by the force component of the j-direction force-measuring branch along the i direction in the global coordinate system, which is called the axial stiffness of the j-direction force-measuring branch; fk,θjIt represents the bending stiffness around k direction caused by the moment component of the j-direction force measuring branch around k direction in the global coordinate system; It represents the average displacement of the i-direction force measuring branch along the i-direction in the global coordinate system; It represents the average displacement of the j-direction force-measuring branch along the i-direction in the global coordinate system; It represents the average value of the bending of the j-direction force-measuring branch around the k-direction in the global coordinate system;

[0024] The non-branching structure index meets the index requirements when the non-branching structure evaluation coefficients in all directions are less than the set evaluation threshold.

[0025] Furthermore, the elastic resistance error coefficient considering the deformation factor in a certain direction is the load-measurement ratio in the certain direction minus 1, and the load-measurement ratio is the ratio of the applied load to the force component synthesized by the force measurement branch.

[0026] Furthermore, the method further comprises:

[0027] 5) Determine a simulation model of the force measurement system using the structural parameters of the force measurement system finally determined in step 4);

[0028] 6) Use the latest simulation model of the force measurement system to evaluate whether the stability of the force measurement system meets the stability requirements: if it does, complete the structural optimization of the entire force measurement system; if it does not, fine-tune the structural parameters of the force measurement system, and use the fine-tuned structural parameters to re-determine the simulation model of the force measurement system, and then re-execute step 6) to iterate until the stability of the force measurement system meets the stability requirements.

[0029] Furthermore, in step 3), the stability is evaluated according to the deformation ratio matrix, and the deformation ratio matrix is:

[0030]

[0031] or

[0032]

[0033] Where U and U e All represent deformation ratio matrices; It represents the average displacement of the x-direction force measuring branch along the y-direction in the global coordinate system; It represents the average displacement of the x-direction force measuring branch in the global coordinate system; It represents the average displacement of the y-direction force-measuring branch along the x-direction in the global coordinate system; The average value of the displacement of the y-direction force-measuring branch in the global coordinate system; It represents the average displacement of the z-direction force measuring branch along the x-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch in the global coordinate system; It represents the average value of the bending of the x-direction force-measuring branch around the y-direction in the global coordinate system; It represents the average value of the bending of the force-measuring branch in the y direction around the x direction in the global coordinate system; It represents the average value of the bending of the z-direction force-measuring branch around the x-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch along the x-direction in the global coordinate system; It represents the average displacement of the y-direction force-measuring branch along the z-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch along the y-direction in the global coordinate system; It represents the average value of the bending of the x-direction force-measuring branch around the z-direction in the global coordinate system; It represents the average value of the bending of the y-direction force-measuring branch around the z-direction in the global coordinate system; It represents the average value of the bending of the z-direction force measuring branch around the y-direction in the global coordinate system.

[0034] Among them, the deformation ratio matrix U e The closer the elements in are to 1, the better the stability of the force measurement system; the closer the elements in the first and third columns in the deformation ratio matrix U are to 1, and the closer the elements in the second and fourth columns are to 0, the better the stability of the force measurement system.

[0035] Furthermore, the stability is evaluated according to the deformation ratio matrix as follows:

[0036] Calculate the deformation ratio matrix U e The trace or norm of U1 is subtracted from the trace or norm of U1 to obtain the corresponding difference. e Corresponding ideal deformation ratio matrix: if the obtained difference is less than the corresponding set difference threshold, it is determined that the stability of the force measurement system meets the stability requirement; otherwise, it is determined that the stability of the force measurement system does not meet the stability requirement; or

[0037] Calculate the matrix UU T The trace or norm of T The trace or norm of is used to obtain the corresponding difference, and U2 is the ideal deformation ratio matrix corresponding to U: if the obtained difference is less than the corresponding set difference threshold, it is determined that the stability of the force measurement system meets the stability requirement; otherwise, it is determined that the stability of the force measurement system does not meet the stability requirement.

[0038] Furthermore, the simulation model of the force measurement branch and the simulation model of the force measurement system are both finite element simulation models.

[0039] In order to solve the above technical problems, the present invention further provides a computer device, including a processor, wherein the processor executes a computer program to implement the steps of the force measurement system structure optimization method introduced above.

[0040] In order to solve the above technical problems, the present invention further provides a force measuring system, which is a force measuring system optimized by the force measuring system structure optimization method introduced above.

[0041] The present invention is an improved invention. The force measurement system structure optimization method, computer device and force measurement system of the present invention take into account that the elastic resistance error is one of the main components of the coupling error, and the structural parameters of the elastic resistance error design are relatively comprehensive. The influence of the axial stiffness and lateral stiffness of the force measurement on the structural performance is considered, and it has a high correlation with the design parameters of the force measurement system. The present invention uses the elastic resistance error as an evaluation index of the structural design to improve the accuracy of the structural design. Moreover, in the process of optimizing the force measurement branch structure in the force measurement system, the elastic resistance error coefficient that ignores the deformation factor is adopted, which can improve the efficiency of the subsequent structural design and optimization of the entire force measurement system. On this basis, the non-force measurement structure other than the force measurement branch is optimized, and each part of the force measurement system is quantitatively designed, which improves the efficiency and accuracy of the force measurement system design. In addition, the present invention is a general structural design method that combines elastic resistance error and simulation, giving full play to the advantages of theoretical methods in analyzing the relationship between structural performance and design parameters in deformation and local load accurate calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flow chart of a force measuring system structure optimization method in an embodiment of the force measuring system structure optimization method of the present invention;

[0043] Figure 2 is a structural diagram of a force measuring system in an embodiment of a force measuring system structure optimization method of the present invention;

[0044] Figure 3 It is a schematic diagram of the influence of torque on the system in the embodiment of the method for optimizing the structure of the force measurement system of the present invention;

[0045] Figure 4 It is a branch force deformation diagram in an embodiment of the force measurement system structure optimization method of the present invention;

[0046] Figure 5 It is a schematic diagram of the force measurement branch layout in an embodiment of the force measurement system structure optimization method of the present invention;

[0047] FIG. 6( a ), FIG. 6( b ) and FIG. 6( c ) are schematic diagrams of different structural parameters of the force measurement branch in the embodiment of the force measurement system structure optimization method of the present invention.

[0048] Explanation of the reference numerals: 1. force measuring system; 2. fixed frame; 3. movable frame; 4. load object; 5. force measuring branch; 6. x-axis movable frame support; 7. x-axis fixed frame support. DETAILED DESCRIPTION

[0049] The present invention takes into account that the elastic resistance error is one of the main components of the coupling error, and the structural parameters of the elastic resistance error design are relatively comprehensive. Considering the influence of the axial stiffness and lateral stiffness of the force measurement on the structural performance, the elastic resistance error is used as an evaluation index of the structural design to improve the accuracy of the structural design. Moreover, in the process of optimizing the force measurement branch structure in the force measurement system, the elastic resistance error coefficient that ignores the deformation factor is adopted, which can improve the efficiency of the subsequent structural design and optimization of the entire force measurement system. In addition, the present invention is a general structural design method that combines elastic resistance error and simulation, giving full play to the advantages of theoretical methods in analyzing the relationship between structural performance and design parameters in deformation and local load accurate calculation. Further, the present invention divides the main structural parameter design of the force measurement system into three parts in the whole scheme: structural parameter optimization of the force measurement branch, structural parameter optimization of the non-branch structure, and structural parameter fine-tuning of the entire force measurement system, and quantitatively designs each part, thereby improving the design efficiency and accuracy of the force measurement system. In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0050] Embodiment of the method for optimizing the structure of the force measurement system:

[0051] Some main terms involved in this embodiment are explained below.

[0052] 1) Coupling error: The coupling error is generally obtained through calibration experiments (also called calibration) to obtain the coupling error matrix. The diagonal elements of the coupling error matrix are called Type I errors, and the non-diagonal elements are called Type II errors. They are key indicators for evaluating the performance of the force measurement system.

[0053] 2) Elastic resistance and interference: The coupling error matrix in the experiment includes multiple factors such as the force measurement system structure, the characteristics of the force measurement element and the environment. The present invention aims to explore the method of designing the force measurement system structure through coupling errors, so it focuses on the coupling errors caused by factors such as structural stiffness and deformation. On this basis, the present invention integrates the existing theoretical concepts of elastic resistance and interference, and makes the following definitions under this framework: In the coupling error matrix involving only structural factors, the diagonal elements that reflect the measurement accuracy of each single dimension are defined as "elastic resistance errors", and those non-diagonal elements that reflect the degree of mutual influence between different dimensions are called "interference errors".

[0054] 3) Non-branch structure: All structures in the force measurement system except the force measurement branch, including the dynamic frame, horizontal force measurement branch support, etc.

[0055] 4) Load-to-measurement ratio: It refers to the ratio of the load applied in one direction to the load borne by the force measuring branch in that direction. Specifically, after the force measuring system applies external force, the axial branch reaction forces of all force measuring branches are extracted, and these branch reaction forces are synthesized into force components in all directions. The load-to-measurement ratio is the ratio of the synthesized force component to the applied force component.

[0056] This embodiment proposes to use the elastic resistance error as a structural forward design indicator to ensure the accuracy of structural analysis and design. In addition, a general structural design method suitable for force measurement systems is proposed, and a theoretical analytical expression reflecting the relationship between the elastic resistance error and the key parameters of the structure is established using the ratio definition method. In order to improve the effectiveness of structural forward design, this embodiment adopts a general structural design method that combines the elastic resistance error with finite element simulation (of course, other simulation software with specific numerical simulation analysis capabilities can also be used). This method determines the structural design parameters of the force measurement system from two aspects: structural stiffness and deformation, and gives full play to the advantages of theoretical methods in analyzing the relationship between structural performance and design parameters and finite element models in accurately calculating deformation and local loads. The contents involved in this method are described in detail below.

[0057] 1. Basic information of force measurement system.

[0058] like Figure 2 As shown, the force measuring system 1 is generally composed of a fixed frame 2, a movable frame 3, a force measuring branch 5 and a supporting system. The core component of the force measuring system 1 is the force measuring branch 5. Each force measuring branch is generally composed of a high-precision uniaxial bidirectional tension and compression force measuring element and two two-axis flexible hinges, which are mainly used to achieve the measurement of axial loads and the release of non-axial loads. Before starting the force measuring system, the load object 4 to be measured (such as an engine) must be firmly installed on the movable frame 2. Subsequently, a known standard external force load is applied to the engine to obtain the calibration coefficient. During the force measuring process, the data collected by each force measuring branch 5 in the force measuring system is converted through the pre-acquired calibration coefficient, which can accurately map the actual load state of the load object, thereby ensuring an accurate assessment of the external load.

[0059] 2. Description of force measurement system coupling.

[0060] The force measurement system synthesizes the load to be measured through the axial force of the branch. In order to express the relationship between the force measurement branch and the measurement component, when measuring a certain load component, the branch that needs to directly synthesize this measurement component is defined as the directly related force measurement branch. On the contrary, the branch that does not synthesize this measurement component is defined as the indirectly related force measurement branch. The mutual influence between the force measurement branch and the measurement component caused by structural deformation is called system coupling, which is composed of elastic resistance and interference. Elastic resistance refers to the load shared by the indirect related force measurement branch during the load measurement process of the direct measurement branch, and interference refers to the additional output generated by the indirect related force measurement branch due to the load.

[0061] The influence of force on the force measurement system is generally simple, mainly manifested as the axial deformation of the directly related force measurement branch and the lateral deformation of the indirectly related force measurement branch. The influence of torque on the system is more complex. The influence of torque on the deformation of the system branch is as follows: Figure 3 The torque measurement process is as follows. Figure 3 The red line in the middle shows that this process involves converting the axial force on the force branch directly related to the target moment load component through an appropriate coefficient relationship to restore the moment load. The moment measurement error is very complex and has two main sources, namely Figure 3 Green lines 1, 2, and 3 are the sources of error generated in the process of restoring the applied moment load by the directly related force measurement branch (the force measurement branch that directly generates the axial force): Green line 1 is the error caused by the bending moment generated by the bending of the end face of the directly related force measurement branch; Green line 2 is the error caused by the bending moment generated by the lateral force of the directly related force measurement branch on the system; Green line 3 is the error caused by the force arm deviation caused by the distribution of the axial force on the end face of the directly related force measurement branch. Figure 3 The blue lines a, b, and c in the middle are the three main factors that cause the torque elastic resistance error: the blue line a is the elastic resistance error caused by the torsion of the branch along the axial direction of the torque in the indirect related force measurement branch; the blue line b is the elastic resistance error caused by the bending moment generated by the indirect related force measurement branch; the blue line c is the elastic resistance error caused by the lateral force generated by the indirect related force measurement branch. Figure 3 The yellow line in the middle is the deformation of the indirect force measurement branch which causes the axial force interference output.

[0062] For force and moment measurement, the synthetic error generated by the direct-related force measurement branch is mainly caused by its own non-axial deformation. The indirect-related force measurement branch mainly shares the axial load of the direct-related force measurement branch through lateral deformation and bending deformation, and the shared load also interferes with its own axial load output.

[0063] 3. Force characteristics of the force measuring branch in the force measuring system.

[0064] Different from the measurement process, the balancing process needs to consider the complete force of each force measuring branch. Each force measuring branch can be simplified as a beam model. Since the axial stiffness of each force measuring branch in the force measuring system is designed to be large, and the lateral stiffness is two orders of magnitude smaller, the deformation of the force measuring branch is mainly the lateral deviation of the end face. When the end face of the force measuring branch is laterally offset and deformed, the force measuring element will generate lateral reaction force and bending moment accordingly. These two forces appear at the same time and maintain a stable correlation, which is a unique feature in the application of vector force measurement systems. This characteristic cannot be considered when studying flexible hinges alone, and the present invention takes this interaction effect into account at the level of complex force measurement systems.

[0065] The main deformation postures of the force measuring branch are as follows: Figure 4 shown. Figure 4 Medium i is the contact point between the i-th force measuring branch and the moving frame, and is also the reference point of the load force rotation; Q i is the contact point between the i-th force measuring branch and the fixed frame, and is also the reference point of the local coordinate system of the force measuring branch; f i is the axial force of the i-th force measuring branch, which is generally equivalent to the measured load of the force measuring branch. The deflection angle of the end face of the force measuring branch in the force measuring system is extremely small and can be ignored. Define the displacement vector of the free end of the i-th force measuring branch as X h,i The load force torque at the free end is W h,i The relationship between the two can be expressed by the branch flexibility matrix C h,i To express:

[0066] X h,i =C h,i W h,i (1)

[0067] The above formula shows that, let the load force rotation W h,i is a unit matrix, then the flexibility matrix can be equivalent to the displacement matrix under unit load. Load force screw W h,i It can be expressed as:

[0068] W h,i =[f h,i m h,i ]=[f x,i f y,i f z,i m x,i m y,i m z,i ] T (2)

[0069] Where f h,i Represents the force vector borne by the end face of the i-th force measuring branch; m h,i represents the moment vector borne by the end face of the i-th force measuring branch; f x,i 、f y,i 、f z,i They represent the force components along the x, y, and z directions borne by the end face of the i-th force measuring branch; m x,i 、m y,i 、m z,i They respectively represent the torque components along the x, y, and z directions borne by the i-th force measuring branch.

[0070] In formula (1), the displacement vector X h,i It can be expressed as:

[0071] X h,i =[u h,i θ h,i ]T =[u x,i ,u y,i ,u z,i ,θ x,i ,θ y,i ,θ z,i ] T (3)

[0072] Where u h,i Represents the displacement deformation vector of the end face of the i-th force measuring branch under the action of external force; θ h,i represents the bending deformation vector of the end face of the i-th force measuring branch under the action of external force; u x,i 、u y,i 、u z,i They represent the displacement components of the end face of the i-th force measuring branch in the x, y, and z directions under the action of external force; θ x,i ,θ y,i ,θ z,i They respectively represent the bending deformation components along the x, y, and z directions generated by the end face of the i-th force measuring branch under the action of external force.

[0073] Assuming that the deformation of the force-measuring branch is within the elastic limit of the linear elastic material, the branch flexibility matrix C in equation (1) can be derived from the beam element strain energy formula. h,i The expression is:

[0074]

[0075] Matrix C h,i The elements in are all flexibility elements. Many researchers have constructed the branch flexibility matrix C based on the second theorem of Castiglione. h,i The mathematical model is obtained and verified by finite element method. Their research shows that the obtained mathematical model is highly consistent with the finite element model. In order to more effectively meet the analysis requirements of complex situations of force measurement branches, the present invention directly extracts C by finite element simulation technology according to formula (5): h,i Flexibility elements to improve the adaptability and accuracy of the analysis.

[0076]

[0077] Stiffness matrix of the branch The series mechanism satisfies the additivity of flexibility, and the parallel mechanism satisfies the additivity of stiffness. Therefore, flexibility is suitable for force measurement branch modeling and analysis, and stiffness is suitable for parallel mechanism modeling and analysis. The stiffness matrix K in the local coordinate system h,i It can be expressed as:

[0078]

[0079] Stiffness matrix K h,iThe elements in are all stiffness elements.

[0080] There are currently two ways to define the flexibility ratio. Definition 1: Establish a flexibility matrix based on the second Cartesian theorem, and establish the corresponding flexibility ratio according to the analysis requirements through the flexibility matrix elements. For example, in order to analyze the relationship between displacement flexibility and rotational flexibility, the flexibility ratio is defined as the ratio of displacement flexibility to rotational flexibility. Method 2: Treat the force measurement branch as a small deformation beam model, calculate the ratio of load to deflection to obtain the flexibility in all directions, and define the ratio of lateral flexibility to axial flexibility as the flexibility ratio. The starting points of the two definitions of the flexibility ratio are different. Method 1 starts from the energy method and has a relatively wide range of analysis and research. Method 2 starts from a simplified equal-section beam and is relatively convenient for engineering calculations. The two are equivalent in practical applications, and the specific process is as follows.

[0081] The deformation of the force branch end face in the force measuring system usually appears as follows Figure 4 The force characteristics of the branch shown in the figure show that the overall rotational displacement of the flexible hinge is close to zero; if the free end rotation angle of the force measuring branch is assumed to be zero, we can obtain:

[0082]

[0083] The flexibility ratio γ of the branch lateral flexibility to the axial flexibility in the force measurement system can be obtained as follows:

[0084]

[0085] where γ y,i is the flexibility of the i-direction force-measuring branch along the y-direction under the condition of limiting the rotational freedom; z,i is the flexibility of the i-direction force measurement branch along the z-direction under the condition of limited rotational freedom. The stiffness of the i-direction force measurement branch along the y-direction under the condition of limited rotational freedom can be defined as K Qy,i ; The stiffness of the i-axis force measurement branch along the z-axis is K Qz,i .

[0086] Formula (8) effectively integrates the two definitions of flexibility ratio in the force measurement system. Therefore, the flexibility ratio of the force measurement branch in the force measurement system can be obtained either through the flexibility matrix or by directly constraining the rotational freedom of the free end of the force measurement branch and extracting the lateral displacement and lateral load of the force measurement branch.

[0087] 4. Measure the load balance and spring resistance of the system.

[0088] For the force measurement system, the essence of elastic resistance (abbreviated as elastic resistance) is that the indirect related force measurement branch generates resistance along the measurement branch direction, reducing the load measured by the measurement direction branch. The force measurement branch is generally simplified to a beam model. For the beam model, the essence of interference is that the force in the non-measurement direction causes the change in the length of the axis of the measurement direction branch, thereby generating additional axial force. Therefore, the relationship between the true value (external load), measurement component, elastic resistance and interference can be expressed as: measurement component true value = output component (composite axial force of force measurement branch) + elastic resistance - interference.

[0089] The measurement model formula is expressed as:

[0090] W P =W s +EW s =W s +(TD)W s (9)

[0091] Where W P is the load force torque, Where P Fx , P Fy , P Fz are the force components of the external load borne by the force measuring system along three orthogonal directions; P Mx , P My , P Mz are the moment components of the external load borne by the force measuring system in three orthogonal directions; W s To measure the force torque, it is synthesized from the axial load of the force measuring branch, W s =[F x F y F z M x M y M z ], where F x 、F y 、F z They represent the force components of the load of the force measuring branch and the reaction force in three orthogonal directions respectively; x 、M y 、M z They represent the moment components of the load synthesized by the force measurement branch reaction force along three orthogonal directions. E is the coupling error coefficient matrix; T is the elastic resistance error coefficient matrix; D is the interference error coefficient matrix. The matrix expressions of the elastic resistance error coefficient matrix T and the interference error coefficient matrix D are:

[0092]

[0093] Where, T f,i (i∈{xyz}) is the force elastic resistance coefficient along the i direction; T m,i(i∈{xyz}) is the moment elastic coefficient around the i-axis; D fi,fj (i,j∈{xyz},i≠j) represents the interference coefficient of the force along the i direction on the force measurement along the j direction; D fi,mj (i,j∈{xyz},i≠j) represents the interference coefficient of the force along the i direction on the torque measurement around the j axis; D mi,fj (i,j∈{xyz},i≠j) represents the interference coefficient of the force around the i-axis on the force measurement along the j-direction; D mi,mj (i,j∈{xyz},i≠j) represents the interference coefficient of the force around the i-axis on the torque measurement around the j-axis. When there is no interference, D is a zero matrix and can be transformed into:

[0094]

[0095] Where I is a column vector whose elements are all 1. The above formula shows that without considering the interference error, the load-measurement ratio of each load component is the same as the description of the elastic resistance, that is, "load-measurement ratio = elastic resistance error coefficient + 1". It should be noted that the elastic resistance error coefficient here is the elastic resistance error coefficient that takes deformation factors into account.

[0096] 5. Elastic resistance error coefficient of force.

[0097] Through simulation, the validity of the coupling analysis model is verified. It is known that the elastic resistance error in the coupling error has a significant correlation with key design parameters such as structural stiffness and deformation. Therefore, the elastic resistance error can be used as a performance indicator of structural design, and the elastic resistance error coefficient expression can be used as a theoretical model for structural analysis and design of the force measurement system. This theoretical model realizes the forward design of the force measurement branch structure parameters based on the expected performance of the force measurement system by associating the elastic resistance error with several key parameters of the force measurement branch, namely the number of branches, axial stiffness, lateral stiffness and end face deformation.

[0098] The spring resistance error coefficient is the ratio of the applied load component to the measured load component of a certain component. Taking the x-direction force load component as an example, the force spring resistance model is established:

[0099]

[0100] In the formula, f x,x The x-direction force measurement branch generates a force along the x-direction, which is an axial force; f x,y The force generated by the y-direction force measuring branch along the x-direction is the lateral force (shear force) of the y-direction force measuring branch; f x,z The force generated by the z-direction force measuring branch along the x-direction is the lateral force (shear force) of the z-direction force measuring branch; the coefficient T fx,yx The elastic resistance error coefficient, which represents the elastic resistance error of the y-direction force measurement branch to the x-direction force measurement, can be expressed as:

[0101]

[0102] Where n y Indicates the number of y-direction force measurement branches; n x Indicates the number of x-direction force measurement branches; K fx,ux The four subscripts in represent the four information of the stiffness. The first subscript f represents the force component, the second subscript x represents the deformation of the branch along the global coordinate x direction, the third subscript u represents the displacement, and the fourth subscript x represents the force measurement branch in the x direction, so K fx,ux represents the displacement stiffness along the x-direction caused by the force component along the x-direction of the x-direction force measuring branch in the global coordinate system; similarly, K fx,uy K represents the displacement stiffness along the x-direction caused by the force component along the x-direction of the y-direction force measuring branch in the global coordinate system; fx,θy It represents the bending stiffness in the x-direction caused by the force component of the y-direction force measuring branch in the global coordinate system; It represents the average displacement of the y-direction force-measuring branch along the x-direction in the global coordinate system; It represents the average displacement of the x-direction force measuring branch in the global coordinate system; It represents the average value of the bending of the y-direction force-measuring branch along the x-direction in the global coordinate system.

[0103] In order to facilitate the description of the structure, the structures such as the moving frame and the support outside the force measurement branch are uniformly defined as non-branch structures. The coupling error is associated with the main design parameters of the structure. Therefore, in theory, the key parameters of the force measurement system can be designed through the coupling error. In order to facilitate the structural design, the elastic resistance model is further improved. Specifically, the axial stiffness K of the interference branch is introduced into the force elastic resistance model shown in formula (14): fy,uy / K fy,uy , we can get:

[0104]

[0105] Therefore, the elastic resistance error coefficient for any component of the force component can be expressed as:

[0106]

[0107] Where n i Indicates the number of force measurement branches in direction i; n j Indicates the number of force measurement branches in the j direction; K fi,ui K represents the displacement stiffness along the i-direction caused by the force component along the i-direction of the i-direction force measuring branch in the global coordinate system; fj,uj K represents the displacement stiffness along the j direction caused by the force component along the j direction of the j-direction force measuring branch in the global coordinate system; fi,ujK represents the displacement stiffness along the i direction caused by the force component of the j-direction force measuring branch along the i direction in the global coordinate system; fk,θj It represents the bending stiffness around k direction caused by the moment component of the j-direction force measuring branch around k direction in the global coordinate system; It represents the average displacement of the i-direction force measuring branch along the i-direction in the global coordinate system; It represents the average displacement of the j-direction force-measuring branch along the i-direction in the global coordinate system; It represents the average value of the bending of the force-measuring branch in the j direction in the global coordinate system.

[0108] There are four main types of ratios in the force-elastic-drag error coefficient shown in formula (16): Ratio 1: Ratio of the number of branches between components n j / n i ; Ratio 2: Component branch axial stiffness ratio K fj,uj / K fi,ui ; Ratio 3: The ratio of the lateral deformation stiffness (i.e. lateral stiffness) of each branch to its axial stiffness K fi,uj / K fj,uj , the ratio of the branch's bending stiffness to its axial stiffness K fk,θj / K fj,uj ; Ratio 4: Deformation ratio u between components in the same direction Gi,j / u Gi,i ,θ Gk,j / u Gi,i Among the four ratios of the elastic resistance error coefficient, ratio 1 can be determined according to the layout requirements or stability requirements; ratio 2 is determined according to the branch load calculation model; ratio 3 is the key design variable, which is the key parameter reflecting the "rigid" and "flexible" configuration of the force measurement branch in the force measurement system, and needs to be designed in accordance with the requirements of all aspects of the flexible hinge; ratio 4 is the ratio of deformation under the assumption of linear elasticity of the material, which is the comprehensive effect of the overall structural form, non-branch structural stiffness and branch stiffness.

[0109] Moreover, without considering the deformation ratio parameter in equation (16), let the displacement deformation ratio in equation (16) be 1 and the angle displacement deformation ratio be 0, that is, In the case of , formula (16) is transformed into:

[0110]

[0111] T in formula (17) fi,ji represents the elastic resistance error coefficient of the j-direction force measurement branch for the i-direction force measurement, ignoring the deformation factor. T in formula (16) fi,ji It represents the elastic resistance error coefficient of the j-direction force measurement branch on the i-direction force measurement taking into account the deformation factor.

[0112] In addition, the finite element model is also needed to design the stiffness and branch layout of the non-branch structure. Finite element analysis can accurately calculate the stress, deformation and local load of the force measurement system structure. The elastic resistance error of the finite element model of the force measurement system is the combined effect of the force measurement branch structure, force measurement branch layout and non-branch structure, while the elastic resistance error coefficient only reflects the elastic resistance error caused by the force measurement branch. Therefore, the difference between the two can reflect the performance of the non-branch structure and the force measurement branch layout.

[0113] 6. Design of non-branching structure stiffness.

[0114] Single-component loads are applied to the three orthogonal directions of the force measurement system, and the ratio of the load in each direction to the force component synthesized by the force measurement branch is defined as the load-measurement ratio. There is no interference error when single-component loading occurs, and the "elastic resistance error coefficient T = load-measurement ratio η" is satisfied at this time. f -1". The axial reaction forces of each force measurement branch are extracted through the finite element model to synthesize the load components borne by the system, and further obtain the load-measurement ratio. Therefore, the concept of load-measurement ratio is more intuitive and convenient for data processing. Therefore, the elastic resistance error coefficient can be calculated through the load-measurement ratio.

[0115] Without considering the deformation ratio parameter in the elastic resistance error coefficient formula, the displacement deformation ratio is set to 1, that is, The angular displacement deformation ratio is 0, that is, The branch number ratio and stiffness ratio are calculated by the finite element model, so as to calculate the elastic resistance error coefficient vector T of the force component without deformation ratio. fw . Force component elastic resistance error coefficient vector T f and the elastic resistance error coefficient vector T without deformation ratio fw The difference can be used to evaluate the stiffness of the non-branch structure, and the difference is defined as the non-branch structure evaluation coefficient vector η t :

[0116] η t =T f -T fw =η f -1-T fw (18)

[0117] Where η t =[η t,x η t,y η t,z ] T , η t,x , η t,y , η t,z are the non-branching structure evaluation coefficients in three orthogonal directions; T f =[T f,x T f,y Tf,z ] T , T f,x 、T f,y 、T f,z are the elastic resistance error coefficients of the force components in three orthogonal directions; T fw =[T fw,x T fw,y T fw,z ] T , T fw,x 、T fw,y 、T fw,z are the elastic resistance error coefficients of the force components without deformation ratio in three orthogonal directions; η f =[η f,x η f,y η f,z ] T , η f,x , η f,y , η f,z They are the force component load ratios in three orthogonal directions.

[0118] η t The measurement deviation caused by the non-force measurement branch caused by factors such as deformation of the structural support components can be evaluated. In the design of a large-load force measurement system, the designer may lack a reasonable grasp of the structural stiffness, η t The stiffness effect of non-branch structures can be evaluated, thus facilitating the stiffness design of non-branch structures such as movable frames and supports.

[0119] 7. Deformation ratio stability and layout design.

[0120] The stability of structural equipment not only involves the ability of the structure to maintain the stability of its structure and function under various conditions, but also includes the performance of the structure under load, dynamic load, thermal change and other conditions. It mainly involves several aspects, including structural stability, elastic stability, dynamic stability, thermal stability, etc. For the force measurement system, stability can be mainly reflected by deformation, so the deformation ratio can reflect the coordination of the deformation of the force measurement branch of the force measurement system and the stability of the overall system. Therefore, the deformation ratio matrix of single-component loading can be used for the stability evaluation of the force measurement system.

[0121] For a force measurement system, whether in the design stage or the later experimental stage, the two types of information that are more convenient to obtain are the axial force of the branch and the deformation displacement of the branch end face. Therefore, elastic resistance and deformation ratio are two better entry angles for structural design and performance analysis. The material itself will have unevenness, processing and assembly will produce shape and position errors, and the connection stiffness of the connection section of the parts will be nonlinear. Many errors will be reflected in the stiffness and ultimately manifested in the form of deformation displacement. The size of the deformation displacement has a strong correlation with the generation of many nonlinear errors.

[0122] Therefore, for general orthogonal compliant force measurement systems and similar mechanisms, stability design from the perspective of deformation is a feasible approach. By extracting the deformation ratio of the spring resistance error coefficient in the above formula (16), the deformation ratio matrix U is obtained as follows:

[0123]

[0124] In the formula, It represents the average displacement of the x-direction force measuring branch along the y-direction in the global coordinate system; It represents the average displacement of the x-direction force measuring branch in the global coordinate system; It represents the average displacement of the y-direction force-measuring branch along the x-direction in the global coordinate system; The average value of the displacement of the y-direction force-measuring branch in the global coordinate system; It represents the average displacement of the z-direction force measuring branch along the x-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch in the global coordinate system; It represents the average value of the bending of the x-direction force-measuring branch around the y-direction in the global coordinate system; It represents the average value of the bending of the force-measuring branch in the y direction around the x direction in the global coordinate system; It represents the average value of the bending of the z-direction force-measuring branch around the x-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch along the x-direction in the global coordinate system; It represents the average displacement of the y-direction force-measuring branch along the z-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch along the y-direction in the global coordinate system; It represents the average value of the bending of the x-direction force-measuring branch around the z-direction in the global coordinate system; It represents the average value of the bending of the y-direction force-measuring branch around the z-direction in the global coordinate system; It represents the average value of the bending of the z-direction force measurement branch around the y-direction in the global coordinate system. In formula (10), the closer the elements of the first and third columns are to 1, and the closer the elements of the second and fourth columns are to 0, the better the stability of the entire force measurement system.

[0125] For the elastic resistance design model of the force measurement system, the angle of the force measurement branch is almost 0, so the deformation ratio matrix shown in equation (19) can be simplified as:

[0126]

[0127] Through U eThe number of branches and branch stiffness performance can be ignored, and only the deformation stability (that is, the stability of the force measurement system claimed in this embodiment) is analyzed, which can improve the deformation stability of the structure. Among them, the closer the elements in formula (20) are to 1, the better the stability of the entire force measurement system.

[0128] Specifically, the effects of different branch layouts can be expressed by the matrix U e The trace or norm of the ideal deformation ratio matrix U1 can be compared and evaluated, or the matrix UU T The trace or norm of T The trace or norm of is used for comparative evaluation, and U2 is the ideal deformation ratio matrix corresponding to U. e The corresponding ideal deformation ratio matrix is The ideal deformation ratio matrix corresponding to U is:

[0129] Taking matrix U as an example, the ideal deformation ratio matrix corresponding to U is Matrix U2U2 T The trace is 6, and the second norm is also 6; if the actual deformation ratio matrix is At this time, the matrix UU T The trace is 8.5922, and the second norm is 8.6393; if the parameters of the first row and first column of the optimization matrix are optimized from 1.21 to 1.11, the actual deformation ratio matrix At this time, the matrix UU T The trace is 8.3709, and the norm is 8.4073. This shows that the trace and norm of the matrix can reflect the effect of optimization. After optimizing multiple deformation ratio parameters, the trace and norm of the matrix can reflect the degree of optimization. At the same time, from a mathematical point of view, the norm of the matrix is ​​used to evaluate the size of the matrix. A large matrix means a large deformation ratio, and thus relatively poor stability (deformation → matrix size → stability). The trace of the matrix is ​​the sum of the eigenvalues. In matrix transformation, the matrix eigenvalue can be regarded as the magnification of a certain dimension, so it can also be used for the trace of the matrix and can also be used to measure the size of the matrix.

[0130] Therefore, when making the corresponding comparison, the specific means may be any one of the following: e If the difference between the trace of U1 and the trace of U2 is small, for example, the difference is less than a certain threshold, then the stability of the force measurement system is determined to meet the stability requirements; if U e The difference between the norm of and the norm of U1 is small, for example, the difference is less than a certain threshold, then the stability of the force measurement system is determined to meet the stability requirements; if UU T The traces and U2U2 T If the difference of the traces is small, for example, the difference is less than a certain threshold, then the stability of the force measurement system is determined to meet the stability requirements; if U2U2T The norm and U2U2 T If the difference in the norm of is small, for example, the difference is less than a certain threshold, it is determined that the stability of the force measurement system meets the stability requirements.

[0131] 8. Method flow.

[0132] Based on the theoretical knowledge introduced above, we can adopt Figure 1 The method flow shown is used to optimize the structure of the force measurement system. The specific steps are as follows:

[0133] 1) Determine the characteristics and index requirements of the force measurement system, and design a preliminary layout plan for the force measurement branches in the force measurement system. The layout plan specifically includes the number of force measurement branches included in the force measurement system, the direction of the force measurement branches, the preliminary layout position of the force measurement branches, the form of flexible hinges in the force measurement branches and other information.

[0134] 2) According to the external load applied in the force measuring system, determine the load range of each force measuring branch, that is, the axial load of each force measuring branch, and then determine the axial stiffness range of the force measuring branches in each direction (specifically, the minimum axial stiffness of the force measuring branches in each direction) according to the structural deformation requirements of all force measuring branches (for example, specifically the axial deformation requirements of the force measuring branches).

[0135] 3) According to the parameters of step 1) and step 2), a finite element model of the force measuring branch in three directions is constructed, and a simulation experiment is carried out in combination with the selected form of the flexible hinge in the force measuring branch, the stiffness range, fatigue strength, and restoring force requirements of the flexible hinge of the force measuring branch, and the structural parameter requirements of the force measuring branch (such as the geometric dimension requirements of the length of the force measuring branch in each direction). During the simulation experiment using the finite element model, the elastic resistance error coefficient (called the force measuring branch index) ignoring the deformation factor in each direction is minimized, and the structural parameters of the force measuring branch are iteratively calculated and adjusted multiple times until convergence, so as to design the stiffness of the force measuring branch (including axial stiffness and lateral stiffness) to obtain the latest force measuring branch structure.

[0136] Here, the elastic resistance error coefficient of a certain direction ignoring deformation factors is the sum of the elastic resistance errors caused by the force measurement branches in the other two directions to the force measurement in that direction. For example, the elastic resistance error coefficient of the x-direction ignoring deformation factors is the sum of the elastic resistance error coefficients of the y-direction and z-direction force measurement branches to the x-direction force measurement. Moreover, the elastic resistance error coefficient of the y-direction force measurement branch to the x-direction force measurement is the product of the ratio of the number of y-direction force measurement branches to the x-direction force measurement branches, the ratio of the axial stiffness of the y-direction force measurement branches to the x-direction force measurement branches, and the ratio of the lateral stiffness of the y-direction force measurement branch to the axial stiffness of the y-direction force measurement branch. The elastic resistance error coefficients of other directions can be derived in this way. The calculation formula of the elastic resistance error coefficient of the y-direction and z-direction force measurement branches to the x-direction force measurement can refer to formula (17), so that the final calculation formula of the elastic resistance error coefficient of the ignoring deformation factors in each direction is:

[0137]

[0138] Moreover, different types of force measuring branches have different structural parameters to be optimized. For example, when the force measuring branch is a cross straight circular force measuring branch, its structural parameters include the overall thickness in the y and z directions, the minimum thickness in the y and z directions, and the length in the x, y, and z directions.

[0139] Among them, in the iterative adjustment process, each time we try to minimize the elastic resistance error coefficients of the three directions ignoring the deformation factor, and the final convergence state means that even if the structural parameters are adjusted again, these three coefficients will no longer decrease or even increase. Moreover, during the adjustment process, we can pay more attention to the coefficients of one or two directions and slightly sacrifice the coefficients of the other directions.

[0140] 4) Based on the latest structural optimization scheme of the force measurement branch, a finite element model of the entire force measurement system is constructed.

[0141] 5) Calculate the load-measurement ratio, and use the load-measurement ratio and the non-branch structure evaluation coefficient vector calculated by formula (18) to optimize the non-branch structure in the optimized force measurement system. The specific process is: calculate the load-measurement ratio η in three orthogonal directions f,x , η f,y , η f,z , and calculate the non-branching structure evaluation coefficients in three orthogonal directions according to formula (18), and determine whether the non-branching structure evaluation coefficients in each direction (i.e., three orthogonal directions) are all less than the set evaluation threshold: if they are not all less than the set evaluation threshold, adjust the structural parameters of the non-branching structure, and re-execute step 5) to iterate until the non-branching structure evaluation coefficients in the three orthogonal directions are all less than the set evaluation threshold.

[0142] Among them, it can be seen from formula (18) that the non-branching structure evaluation coefficients in the x, y, and z directions are the elastic resistance error coefficients T considering the deformation factor in the x, y, and z directions respectively f,x 、T f,y 、T f,z Corresponding to the elastic resistance error coefficient T in x, y, and z directions ignoring deformation factors fw,x 、T fw,y 、T fw,z Moreover, combined with the section “IV. Load balance and elastic resistance of the measurement system”, it can be seen that the elastic resistance error coefficient T considering the deformation factor is f,x 、T f,y 、T f,z And they are equal to the load-to-measure ratio in the corresponding direction minus 1, that is, η f,x -1, η f,y -1, η f,z -1.

[0143] The optimization goal here is set to that the non-branching structure evaluation coefficients in the three orthogonal directions are all less than the set evaluation threshold rather than that the non-branching structure evaluation coefficients in the three orthogonal directions are all minimized. This is because when the evaluation coefficients in the three directions are all minimized, the cost of the entire force measurement system will be higher, and the target can be achieved without minimizing the evaluation coefficients in the three directions.

[0144] 6) After optimizing the non-branch structure, perform force measurement branch deformation extraction to obtain the deformation ratio matrix U e , refer to formula (20). The deformation ratio matrix is ​​used to evaluate whether the stability of the force measurement system meets the stability requirements: when the stability does not meet the requirements, the structural parameters of the force measurement system are modified and adjusted. Here, the structural parameters of the force measurement system include the structural parameters of the branch structure mentioned in step 3) and the structural parameters of the non-branch structure mentioned in step 5). The adjustment here is different from the adjustment in step 3) and step 5). The adjustment here is fine-tuning, and step 6) is re-executed for iteration until the stability of the force measurement system meets the requirements. When the stability meets the stability requirements, the design optimization of the structural parameters of the force measurement system is completed.

[0145] Among them, the deformation ratio matrix is ​​selected as U in formula (20): e When the stability of the force measurement system meets the requirements, it means that the elements in the deformation ratio matrix are as close to 1 as possible, which can be specifically measured using U e The trace or norm of U e The optimization result is judged by the difference of the trace or norm of the corresponding ideal deformation ratio matrix U1. Of course, when the deformation ratio matrix is ​​selected as U in formula (19), the stability of the system can be evaluated according to the content introduced in "VII. Deformation ratio stability and layout design".

[0146] It should be noted that the content of step 6) is to consider the influence of deformation on the entire force measurement system when the stiffness is well designed. Moreover, in the whole scheme, only the spring resistance error is selected for the force measurement system design because the correlation between the interference error and the structural parameters is very low.

[0147] IX. Verification instructions.

[0148] The method of the present invention is described in detail below using a force measurement system as an example. The design indicators include: (1) axial force (P x ) load is 150 kN, the in-situ calibration uncertainty is 1% FS; (2) normal force (P y ) Load is -100 kN, in-situ calibration uncertainty is 1.5% FS; (3) Pitch moment (M z ) is 50 kN·m, and the uncertainty of in-situ calibration is 1.5% FS; (4) the lateral force (Pz) is 50 kN; (5) the height of the engine from the installation plane is 2.6 m; (6) the interference between the two components is less than 5%, and the combined interference is less than 10%; (7) the model weight is 100 kN.

[0149] 1) Select the force measurement branch layout.

[0150] The characteristic of the force measurement system test is that the load center is higher than the surface of the force measurement system, while the structural requirements are usually small. In order to ensure the support stability, 4 groups of force measurement branches are designed in the y direction, and 4 points of outer support are used to maximize the support effect. 2 groups of force measurement branches are designed in the x direction, and 2 groups of force measurement branches are designed in the z direction. According to the analysis results of the symmetrical arrangement of the horizontal units, the x-direction and z-direction force measurement branches are distributed symmetrically on the inner side of the lower part of the moving frame. The basic layout is as follows Figure 5 As shown, x5 and x8 are x-direction force measuring branches, y1 to y4 are y-direction force measuring branches, z7 and z8 are z-direction force measuring branches, 6 is an x-direction movable frame support, and 7 is an x-direction fixed frame support.

[0151] The specific information of the layout coordinates of the force measurement branch is shown in Table 1. The static mapping matrix G s The center position vector uses the fixed frame coordinates, and the origin of the coordinates is set as the center of the bottom surface of the fixed frame. The overall layout mainly considers the load stability and moment measurement requirements. Figure 5 In the layout of Table 1, i represents Figure 5 The information of each force measurement branch mainly includes the connection coordinates r si , and the coordinates connected with the movable frame t si , force direction s si .

[0152] Table 1 Force measurement branch information table

[0153] i <![CDATA[r si / (mm)]]> <![CDATA[t si / (mm)]]> <![CDATA[s si / (m)]]> 1 (-1360,100,-320) (-1360,635,-320) (0，1，0) 2 (-1360,100,320) (-1360,635,320) (0，1，0) 3 (1360,100,320) (1360,635,320) (0，1，0) 4 (1360,100,-320) (1360,635,-320) (0，1，0) 5 (-470,390,-300) (-40,390,-300) (1，0,0) 6 (470,390,300) (40,390,300) (-1，0，0) 7 (-1100,515，180) (-1100,515，-180) (0，0，-1) 8 (1100,515，-180) (1100,515，180) (0，0，1)

[0154] 2) Design of force measurement branch structure in the force measurement system.

[0155] The external load force of the force measuring system including gravity can be expressed as:

[0156] W s =[150000 -200000 50000 167500 0-552500](N) (22)

[0157] The axial load f of the eight force measuring branches can be obtained according to the following expression s :

[0158]

[0159] In the formula Calculated from the data in Table 1; K s =diag(k1 k2 …k8), k1, k2 …k8 are the axial stiffness of the eight force measurement branches, which can be assigned large values ​​at the beginning, such as 1×10 9 N / m.

[0160] According to formula (18), the axial loads of the eight branches of the eight-branch force measurement system under the given load conditions are:

[0161] =[151551 -69933 -251550 -30067 75000 -75000 -25000 25000](N) (24)

[0162] In order to reduce the deformation error, the axial deformation of all force measuring branches is limited to less than 0.5mm, so the minimum axial stiffness of the force measuring branches in the three directions is:

[0163] K s =diag([1.5×10 8 3×10 8 0.5×10 8 ])(N / m) (25)

[0164] The load ranges in the three directions are quite different, so a force measurement branch with symmetrically arranged flexible hinges is selected.

[0165] Referring to formula (21), the elastic resistance error coefficient of the eight-branch force measurement system ignoring the deformation factor is expressed as:

[0166]

[0167] With the goal of minimizing the elastic resistance error coefficient ignoring deformation factors in three directions, the structural parameters of the force measuring branch are adjusted in combination with finite element simulation. During the design process, it is necessary to ensure that the flexible hinge of the force measuring branch has sufficient design stiffness and fatigue strength, and sufficient deformation recovery force needs to be reserved.

[0168] Considering the measurement requirements, actual working conditions and processing convenience, the symmetrical cross straight circle force measuring branch is selected. The main parameters of the symmetrical cross straight circle force measuring branch include 7, including the overall thickness a y 、a z , minimum thickness c z 、c y and length l x , l y , l z ,like Figure 6(a) to Figure 6(c) Through the finite element model, the design parameters were adjusted and iterated many times, and the structural parameters of the force measurement branches in three orthogonal directions were obtained as shown in Table 2.

[0169] Table 2 Force measurement branch parameters

[0170] direction x / (m) y / (m) z / (m) <![CDATA[a y ]]> 0.13 0.15 0.1 <![CDATA[a z ]]> 0.13 0.15 0.1 <![CDATA[c y ]]> 0.02 0.02 0.013 <![CDATA[C z ]]> 0.02 0.02 0.013 <![CDATA[l x ]]> 0.47 0.535 0.36 <![CDATA[l y ]]> 0.33 0.4 0.25 <![CDATA[l z ]]> 0.125 0.14 0.105

[0171] The axial stiffness (K Qx，j ) and lateral deformation stiffness (K Qy,j , K Qz，j ). When obtaining the stiffness of the force-measuring branch, only the displacement in the j direction of the force-measuring branch end face is set to a free state, and the displacement in the other directions is set to a constant of 0.

[0172] According to the measurement requirements, the x-axis measurement accuracy requirement is relatively high. Therefore, in the process of configuring the lateral flexibility of the force measurement branch, the elastic resistance error coefficient T of the x-axis ignoring the deformation factor should be reduced as much as possible while meeting the overall requirements. fw，x After repeated optimization design, the axial stiffness and lateral deformation stiffness of the force measuring branch are obtained as shown in the table.

[0173] Table 3 Stiffness of the force measurement branch in the local coordinate system

[0174] j <![CDATA[k Qj，x / (N / m)]]> <![CDATA[k Qj，y / (N / m)]]> <![CDATA[k Qj，z / (N / m)]]> x 5.664×108 1.354×106 3.144×106 y 6.141×108 4.011×106 4.556×106 z 1.658×108 1.921×106 1.966×106

[0175] The material selection of the flexible hinge mainly considers the material restoring force and linear elastic stability. The material with small internal energy consumption and small creep is preferred. The cobalt and chromium components in high-purity metals and alloys can strengthen the material lattice and reduce dislocations. The heat treatment process can change the microstructure of the material and enhance the structural stability. Therefore, 60Si2Cr is selected as the material of the flexible hinge in the force measurement branch. At the same time, the above structure meets the fatigue strength requirements under the full load axial force and the lateral load of 5% of the axial force.

[0176] 3) Non-branch structure stiffness design.

[0177] The structures such as the moving frame and the support outside the force measurement branch are uniformly defined as non-branch structures. When the axial stiffness and flexibility of the force measurement branch are optimized to a certain extent, it is necessary to optimize the stiffness of the non-branch structure. The non-branch structure stiffness is optimized by taking the deviation of the elastic resistance error coefficient considering the deformation factor and the elastic resistance error coefficient ignoring the deformation factor as the optimization target, and finally the elastic resistance error coefficient contribution η of the non-branch structure is obtained. t，i (i.e., η in Table 4 t ) and related information are shown in Table 4.

[0178] Table 4 Load-to-measure ratio design and structural stiffness design

[0179] direction <![CDATA[T fw，i ]]> <![CDATA[η f，i ]]> <![CDATA[T fe，i ]]> <![CDATA[η t ]]> x 0.0176 1.042405 0.042405 0.024805 y 0.0027 1.007291 0.007291 0.004591 z 0.0739 1.085018 0.085018 0.011118

[0180] Some people believe that the stiffness of the force measurement branch when analyzed separately is different from that when loaded in the force measurement system, so the separate design is inaccurate. This phenomenon is mainly caused by the load distribution of the force measurement branch. Therefore, during the simulation of the force measurement branch, a rigid body is placed on its free end face and some degrees of freedom of the rigid body are restricted. This setting ensures the consistency between the separate analysis performance of the force measurement branch and the actual performance in the force measurement system.

[0181] 4) Stability analysis of the force measurement system.

[0182] A single-component remote force is applied to the force measuring system, the surface of the moving frame is selected as the action surface, the large deflection setting is turned on, and the remote loads in three directions are applied to the center of the distribution circle of the force measuring branch in each direction. The axial force, shear force and bending moment of the beam connection unit of each force measuring branch are obtained respectively. When the y-direction load component is loaded, a rectangular block is placed on the upper surface of the moving frame to act as a mounting frame. The rectangular block is set as a rigid body, and the load is applied. The force and deformation of the 8 force measuring branches are collected. The specific information is shown in Tables 5, 7 and 9. The "force measuring element" will bear a certain shear force and bending moment, and the magnitude of the shear force is related to the branch stiffness ratio between the components of the non-measurement direction load and the flexible hinge and the flexibility ratio of the force measuring branch. This is also a major advantage of the elastic resistance error coefficient in characterizing structural performance in a proportional form.

[0183] In order to approach the working condition of the model to be tested being consolidated on the upper surface of the moving frame, a rectangular block is placed on the upper surface of the moving frame to act as a mounting frame when simulating the loading of the y-axis load component. The rectangular block is set as a rigid body, and the load is applied to collect the force and deformation of the 8 force measuring branches. At the same time, the deformation displacement at the end face of each force measuring branch is obtained. The specific information is shown in Table 6, Table 8 and Table 10. The deformation range of the designed force measuring system is within 0.4 mm, which meets the required deformation requirement within 0.5 mm.

[0184] Table 5 "P x =150kN” branch force

[0185]

[0186] Table 6 "P x =150kN” branch deformation displacement

[0187]

[0188] Table 7 "P y =100kN” branch force

[0189]

[0190]

[0191] Table 8"P y =100kN" branch deformation

[0192]

[0193] Table 9"P z =50kN” branch force

[0194]

[0195] Table 10"P z =50kN" branch deformation

[0196]

[0197] Observing Table 7, we find that the data of the force measurement branches caused by the y-direction in the x-direction and z-direction are relatively large, but the central symmetric structure makes the y-direction load have little interference on the force measurement components in the x-direction and z-direction after the components are synthesized. The average data of the branch deformation in the three directions are calculated from the data in Tables 6, 8 and 10, and the deformation ratio matrix is ​​further obtained as follows:

[0198]

[0199] The deformation ratio matrix shown in formula (27) reaches a relatively suitable state. If the influence of factors such as size is released, the deformation ratio matrix can be further optimized.

[0200] Embodiment of the method for optimizing the force measurement branch structure in the force measurement system:

[0201] The core idea of ​​the embodiment of the method for optimizing the structure of a force measuring branch in a force measuring system of the present invention is to use the elastic resistance error ignoring the deformation factor as an optimization index to optimize the structure of the force measuring branch in the force measuring system to ensure the accuracy of structural analysis and design. The specific optimization process can be seen in steps 1) to 3) of "Eight, Method Flow" of the embodiment of the method for optimizing the structure of the force measuring system, which will not be repeated in this embodiment.

[0202] Computer device embodiment 1:

[0203] A computer device embodiment of the present invention includes a memory, a processor, an internal bus and a computer program stored in the memory, and the processor and the memory communicate and exchange data with each other through the internal bus. The processor executes the computer program to implement the steps of a force measurement system structure optimization method introduced in the embodiment of the force measurement system structure optimization method of the present invention. Among them, the processor can be a processing device such as a microprocessor MCU, a programmable logic device FPGA, etc.; the memory can be various memories that use electrical energy to store information, such as RAM, ROM, etc., or it can be a memory that uses other methods.

[0204] Computer device embodiment 2:

[0205] A computer device embodiment of the present invention includes a memory, a processor, an internal bus and a computer program stored in the memory, and the processor and the memory communicate and exchange data with each other through the internal bus. The processor executes the computer program to implement the steps of a force measurement branch structure optimization method in a force measurement system introduced in the embodiment of the force measurement branch structure optimization method in the force measurement system of the present invention. The processor can be a processing device such as a microprocessor MCU, a programmable logic device FPGA, etc.; the memory can be various memories that use electrical energy to store information, such as RAM, ROM, etc., or it can be a memory using other methods.

[0206] Force measurement system embodiment:

[0207] A force measuring system embodiment of the present invention is a force measuring system designed according to a force measuring system structure optimization method introduced in the force measuring system structure optimization method embodiment. The specific detailed process of the method has been described in detail in the force measuring system structure optimization method embodiment, and will not be repeated in this embodiment.

[0208] In summary, the present invention has the following characteristics: 1) The forward design index, the spring resistance error, which is strongly associated with the structural parameters of the force measurement system, is used to establish a theoretical analytical expression reflecting the relationship between the spring resistance error and the key structural parameters. The spring resistance error is one of the main components of the coupling error. The structural parameters involved in the spring resistance error are relatively comprehensive and have a high correlation with the structural parameters of the force measurement system, which can ensure the accuracy of structural analysis and design. 2) The present invention fully combines theoretical design with finite element models, which can improve the effectiveness of structural forward design, determine the structural design parameters of the force measurement system from the two aspects of structural stiffness and deformation, and give full play to the advantages of theoretical methods in analyzing the relationship between structural performance and design parameters and finite element models in accurate calculation of deformation and local loads. 3) In the entire scheme, the design of the main structural parameters of the force measurement system is divided into three parts: structural parameter optimization of the force measurement branch, structural parameter optimization of the non-branch structure, and structural parameter fine-tuning of the entire force measurement system, and each part is quantitatively designed, which improves the design efficiency and accuracy of the force measurement system.

[0209] Specific implementation methods are given above, but the present invention is not limited to the described implementation methods. The basic idea of ​​the present invention lies in the above basic scheme. For ordinary technicians in this field, it does not take creative work to design various deformed models, formulas, and parameters according to the teachings of the present invention. Changes, modifications, substitutions, and variations of the implementation methods without departing from the principles and spirit of the present invention still fall within the scope of protection of the present invention.

Claims

1. A method for optimizing the force measurement branch structure in a force measurement system, characterized in that: The method includes: 1) Constructing a simulation model of the force measurement branch according to the initial structural parameters of the force measurement branch; 2) Using the latest simulation model of the force measurement branch to determine whether the force measurement branch index has converged: if it has converged, the structural parameters of the force measurement branch are optimal at this time; otherwise, the structural parameters of the force measurement branch are adjusted to reduce the force measurement branch index and the simulation model of the force measurement branch is re-determined, and then step 2) is re-executed to iterate until convergence; The force measuring branch index is the elastic resistance error coefficient of ignoring deformation factors in three directions; wherein the elastic resistance error coefficient of ignoring deformation factors in a certain direction is the sum of the elastic resistance error coefficients of ignoring deformation factors generated by the other two force measuring branches for the force measurement in the certain direction, and the elastic resistance error coefficient of ignoring deformation factors generated by the other force measuring branches for the force measurement in the certain direction is the product of the ratio of the number of the other force measuring branches in the one direction to the force measuring branches in the one direction, the ratio of the axial stiffness of the other force measuring branches in the one direction to the force measuring branches in the one direction, and the ratio of the lateral stiffness of the other force measuring branches in the one direction to the axial stiffness of the other force measuring branches in the one direction.

2. The method for optimizing the force measurement branch structure in the force measurement system according to claim 1, characterized in that: The simulation model is a finite element simulation model.

3. A computer device comprising a processor, characterized in that: The processor executes the computer program to implement the steps of the method according to claim 1 or 2.

4. A method for optimizing the structure of a force measurement system, characterized in that: The method includes: 1) Constructing a simulation model of the force measuring branch in the force measuring system according to the initial structural parameters of the force measuring branch; 2) Using the latest simulation model of the force measurement branch to determine whether the force measurement branch index has converged: if not, adjusting the structural parameters of the force measurement branch to reduce the force measurement branch index and re-determining the simulation model of the force measurement branch, and then re-execute step 2) to iterate until convergence; if converged, execute step 3); The force measurement branch index is the elastic resistance error coefficient of ignoring deformation factors in three directions; wherein, the elastic resistance error coefficient of ignoring deformation factors in a certain direction is the sum of the elastic resistance error coefficients of ignoring deformation factors generated by the remaining two force measurement branches for the force measurement in the certain direction, and the elastic resistance error coefficient of ignoring deformation factors generated by the remaining one-way force measurement branches for the force measurement in the certain direction is the product of the ratio of the number of the remaining one-way force measurement branches to the force measurement branches in the certain direction, the ratio of the axial stiffness of the remaining one-way force measurement branches to the force measurement branches in the certain direction, and the ratio of the lateral stiffness of the remaining one-way force measurement branches to the axial stiffness of the remaining one-way force measurement branches; 3) constructing a simulation model of the force measurement system according to the initial structural parameters of the non-branch structure and the structural parameters of the force measurement branch finally determined in step 2); wherein the non-branch structure is the structure in the force measurement system other than the force measurement branch; 4) Use the latest simulation model of the force measurement system to determine whether the non-branch structure indicators meet the index requirements: if so, the structural parameters of the non-branch structure are optimal at this time; if not, adjust the structural parameters of the non-branch structure and re-determine the simulation model of the force measurement system, and then re-execute step 4) to iterate until the non-branch structure indicators meet the index requirements.

5. The method for optimizing the structure of a force measurement system according to claim 4, characterized in that: In step 4), the non-branching structure index is the non-branching structure evaluation coefficient in each direction, and the non-branching structure evaluation coefficient in a certain direction is the difference between the elastic resistance error coefficient in the certain direction considering the deformation factor and the elastic resistance error coefficient in the certain direction ignoring the deformation factor; The elastic resistance error coefficient considering deformation factor in a certain direction is the sum of the elastic resistance error coefficients considering deformation factor generated by the force measurement branches in the other two directions for the force measurement in the certain direction, and the elastic resistance error coefficient considering deformation factor is: Where, T fi,ji It represents the elastic resistance error coefficient of the i-direction force measurement branch on the y-direction force measurement; n i Indicates the number of force measurement branches in direction i; n j Indicates the number of force measurement branches in the j direction; K fi,ui It represents the displacement stiffness along the i-direction caused by the force component of the i-direction force-measuring branch in the global coordinate system, which is called the axial stiffness of the i-direction force-measuring branch; K fj,uj K represents the displacement stiffness along the j direction caused by the force component of the j-direction force-measuring branch in the global coordinate system, which is called the axial stiffness of the j-direction force-measuring branch; fi,uj K represents the displacement stiffness along the i direction caused by the force component of the j-direction force-measuring branch along the i direction in the global coordinate system, which is called the axial stiffness of the j-direction force-measuring branch; fk,θj It represents the bending stiffness around k direction caused by the moment component of the j-direction force measuring branch around k direction in the global coordinate system; It represents the average displacement of the i-direction force measuring branch along the i-direction in the global coordinate system; It represents the average displacement of the j-direction force-measuring branch along the i-direction in the global coordinate system; It represents the average value of the bending of the j-direction force-measuring branch around the k-direction in the global coordinate system; The non-branching structure index meets the index requirements when the non-branching structure evaluation coefficients in all directions are less than the set evaluation threshold.

6. The method for optimizing the structure of a force measurement system according to claim 5, characterized in that: The elastic resistance error coefficient considering deformation factors in a certain direction is the load-measurement ratio in that direction minus 1. The load-measurement ratio is the ratio of the applied load to the force component synthesized by the force measuring branch.

7. The method for optimizing the structure of a force measurement system according to any one of claims 4 to 6, characterized in that: The method further includes: 5) Determine a simulation model of the force measurement system using the structural parameters of the force measurement system finally determined in step 4); 6) Use the latest simulation model of the force measurement system to evaluate whether the stability of the force measurement system meets the stability requirements: if it does, complete the structural optimization of the entire force measurement system; if it does not, fine-tune the structural parameters of the force measurement system, and use the fine-tuned structural parameters to re-determine the simulation model of the force measurement system, and then re-execute step 6) to iterate until the stability of the force measurement system meets the stability requirements.

8. The method for optimizing the structure of a force measurement system according to claim 7, characterized in that: In step 3), the stability is evaluated according to the deformation ratio matrix, and the deformation ratio matrix is: or Where U and U e All represent deformation ratio matrices; represents the average displacement of the x-direction force measuring branch along the y-direction in the global coordinate system; u Gx,x It represents the average displacement of the x-direction force measuring branch in the global coordinate system; represents the average displacement of the y-direction force-measuring branch along the x-direction in the global coordinate system; u Gy,y The average value of the displacement of the y-direction force-measuring branch in the global coordinate system; u Gx,z It represents the average displacement of the z-direction force measuring branch along the x-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch in the global coordinate system; It represents the average value of the bending of the x-direction force-measuring branch around the y-direction in the global coordinate system; It represents the average value of the bending of the force-measuring branch in the y direction around the x direction in the global coordinate system; It represents the average value of the bending of the z-direction force-measuring branch around the x-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch along the x-direction in the global coordinate system; It represents the average displacement of the y-direction force-measuring branch along the z-direction in the global coordinate system; It represents the average displacement of the z-direction force measuring branch along the y-direction in the global coordinate system; It represents the average value of the bending of the x-direction force-measuring branch around the z-direction in the global coordinate system; It represents the average value of the bending of the y-direction force-measuring branch around the z-direction in the global coordinate system; It represents the average value of the bending of the z-direction force-measuring branch around the y-direction in the global coordinate system; Among them, the deformation ratio matrix U e The closer the elements in are to 1, the better the stability of the force measurement system; the closer the elements in the first and third columns in the deformation ratio matrix U are to 1, and the closer the elements in the second and fourth columns are to 0, the better the stability of the force measurement system.

9. The method for optimizing the structure of a force measurement system according to claim 8, characterized in that: The way to evaluate stability based on the deformation ratio matrix is: Calculate the deformation ratio matrix U e The trace or norm of U1 is subtracted from the trace or norm of U1 to obtain the corresponding difference. e Corresponding ideal deformation ratio matrix: if the obtained difference is less than the corresponding set difference threshold, it is determined that the stability of the force measurement system meets the stability requirements; otherwise, it is determined that the stability of the force measurement system does not meet the stability requirements; or Calculate the matrix UU T The trace or norm of T The trace or norm of is used to obtain the corresponding difference, and U2 is the ideal deformation ratio matrix corresponding to U: if the obtained difference is less than the corresponding set difference threshold, it is determined that the stability of the force measurement system meets the stability requirement; otherwise, it is determined that the stability of the force measurement system does not meet the stability requirement.

10. The method for optimizing the structure of a force measurement system according to any one of claims 4 to 6, characterized in that: The simulation model of the force measurement branch and the simulation model of the force measurement system are both finite element simulation models.

11. A computer device comprising a processor, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 4 to 10.

12. A force measuring system, characterized in that: The force measuring system is a force measuring system optimized by the method according to any one of claims 4 to 10.

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