A micro-clamping force indirect measurement system and method thereof

Abstract

This invention discloses a micro-clamping force indirect measurement system and method. The system includes a drive system, a force sensor, a single-force input single-stage compliant orthogonal displacement amplification mechanism, a microscopic vision measurement system, a data acquisition module, and a data processing module. The method includes: acquiring the input force through a force sensor located at the input end of the drive, and simultaneously acquiring the actual displacement of point B at the output end of the mechanism along the output direction through the microscopic vision measurement system. The input force and output displacement are used as input quantities, which are substituted into a pre-established semi-analytical model by the data processing module to obtain the corresponding micro-clamping force. This invention enables non-invasive measurement of micro-clamping force without the need for additional force measurement structures. As a micro-clamping force indirect measurement system and method, this invention can be widely applied in the field of precision measurement technology.

Description

Technical Field

[0001] This invention relates to the field of precision measurement technology, and in particular to a micro-clamping force indirect measurement system and method thereof. Background Technology

[0002] In the field of precision engineering, microgrippers, as important end-effectors in micro-operating systems, directly affect the safety, stability, and operational accuracy of the manipulated object through their clamping force. For objects such as brittle micro-components, flexible micro-devices, and biological samples, excessive clamping force can easily cause damage, while insufficient clamping force can easily lead to target slippage or operational failure. Therefore, accurate measurement of micro-clamping force is of great significance.

[0003] Existing methods for measuring micro-clamping force mainly include direct measurement methods and indirect measurement methods. Direct measurement methods typically acquire force information by placing micro-force sensors at the clamping end or in the force transmission path. However, this type of method has problems such as limited sensor size, complex assembly, and high cost. Especially in miniaturized micro-clamping systems, the addition of force measuring structures can easily change the stiffness distribution, flexibility matching relationship, and force transmission path of the original mechanism, thereby affecting the working performance of the mechanism itself.

[0004] Indirect measurement methods typically combine structural displacement, strain, or other intermediate physical quantities with model inversion to derive clamping force, offering the advantage of being more non-invasive compared to direct measurement methods. However, some existing indirect measurement schemes rely on additional sensitive structures, extra displacement amplification structures, or empirical calibration models, which can still affect the original structural characteristics to varying degrees, or suffer from problems such as weak model applicability and insufficient accuracy.

[0005] In micro-gripper transmission mechanisms, single-force input, single-stage compliant orthogonal displacement amplification mechanisms require only input from one side of the driver to achieve orthogonal displacement conversion, thereby realizing the parallel clamping motion of the grippers. However, the working mechanism of this system relies on high-precision compliance matching, and its displacement conversion performance is highly sensitive to the flexibility coefficient of the flexible beam and the distribution of structural parameters. Adding an additional force-measuring structure to such mechanisms can easily damage their original mechanical properties.

[0006] In summary, the related technologies for micro-clamping force measurement suffer from several problems, including difficulties in sensor integration, the potential for additional force measuring structures to disrupt the original mechanical properties of the compliant mechanism, and insufficient measurement accuracy of purely analytical models. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a micro-clamping force indirect measurement system and method, which enables non-invasive measurement of micro-clamping force without the need for additional force measuring structures.

[0008] The first technical solution adopted in this invention is: a micro-clamping force indirect measurement system, comprising a driving system, a force sensor, a single-force input single-stage compliant orthogonal displacement amplification mechanism, a microscopic vision measurement system, a data acquisition module, and a data processing module. The force sensor is arranged at the input end of the single-force input single-stage compliant orthogonal displacement amplification mechanism. The driving system is positioned opposite to the single-force input single-stage compliant orthogonal displacement amplification mechanism. The microscopic vision measurement system is located at the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism. The data acquisition module is electrically connected to the force sensor. The data processing module is signal-connected to both the microscopic vision measurement system and the data acquisition module. The drive system includes a piezoelectric actuator for applying an input force to a single-force input single-stage compliant orthogonal displacement amplification mechanism; The force sensor is used to detect the input force; The single-force input single-stage compliant orthogonal displacement amplification mechanism is used to generate corresponding orthogonal displacements based on the input force and to form a micro-clamping force; The microscopic visual measurement system includes a CCD camera and a camera lens, used to acquire image information from the output end of a single-force input single-stage compliant orthogonal displacement amplification mechanism; The data acquisition module is used to acquire signals of input force. The data processing module is used to calculate the actual displacement based on the image information of the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism, and to obtain the micro-clamping force based on the input force and the actual displacement.

[0009] Furthermore, the single-force input single-stage compliant orthogonal displacement amplification mechanism is a symmetrical mechanism based on the triangular amplification principle. Specifically, it includes a first flexible beam, a second flexible beam, an input end rigid body beam, an output end rigid body, and a jaw. The first flexible beam and the second flexible beam are respectively connected between the input end rigid body beam and the output end rigid body, forming the compliant force transmission structure of the mechanism. After the drive system applies an input force to the input end, the input force is transmitted to the first flexible beam and the second flexible beam through the input end rigid body beam. The transmission and conversion of force and displacement are realized through the elastic deformation of the flexible beams, causing the output end rigid body to generate orthogonal displacement and forming a micro-clamping force at the jaw.

[0010] Furthermore, the micro-clamping force indirect measurement system also includes a vibration isolation table, a three-degree-of-freedom adjustment platform, a connecting base, a camera bracket, a mechanism base, and a pre-tightening device. The connecting base is fixedly connected to the vibration isolation table, the three-degree-of-freedom adjustment platform is disposed on the connecting base, the mechanism base is disposed on the three-degree-of-freedom adjustment platform, the single-force input single-stage compliant orthogonal displacement amplification mechanism is disposed on the mechanism base by fixing bolts, the camera bracket is disposed on the vibration isolation table, the CCD camera and camera lens are mounted on the camera bracket, and the piezoelectric actuator is disposed on the mechanism base by the pre-tightening device. The pre-tightening device is disposed on the mechanism base and cooperates with the force sensor so that the force sensor is located between the piezoelectric actuator and the mechanism input end.

[0011] The second technical solution adopted in this invention is: a method for indirect measurement of micro-clamping force in a micro-clamping force indirect measurement system, comprising the following steps: Based on the preset beam size parameter design equation, the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism are determined, and a coupling relationship model between the input force, the output displacement and the micro clamping force is constructed. Based on the coupling relationship model, an analytical model is derived to show the relationship between the theoretical displacement at the output end and the input force and micro-clamping force. Finite element error analysis was performed on the analytical model to obtain the relationship between the analytical model and the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism. The dimensionless factor and correction coefficient were constructed using the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism to build a semi-analytical model for indirect measurement of micro clamping force. Acquire input force information and input the input force information into a single-force input single-stage compliant orthogonal displacement amplification mechanism to obtain the actual displacement at the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism; The input force information and actual displacement are input into a semi-analytical model for indirect measurement of micro-clamping force to obtain the micro-clamping force.

[0012] Furthermore, the expression for the preset beam dimension parameter design equation is as follows: ; In the above formula, Indicates the rigid body at the output end. Orthogonal displacement output direction displacement, Indicates the rigid body at the output end. Displacement in direction, Indicates the rigid body at the output end. Displacement in direction, This represents the theoretical displacement amplification factor of the mechanism. , This represents the torque-to-linear displacement conversion factor of the mechanism. This represents the normalized unit input force applied at the input terminal. This represents the characteristic length parameter of the rigid beam at the input end. Indicates the connection point between the first flexible beam and the rigid body at the output end. rigid body center of mass at the output end Feature distance, This indicates the magnification ratio of the mechanism. , This represents the compliant hinge angle correction factor for the first flexible beam.

[0013] Furthermore, the coupling relationship model is established based on the static equilibrium equation, the deformation compatibility equation, the load distribution method for statically indeterminate structures, and Castiglione's second theorem.

[0014] Furthermore, the specific expression of the analytical model relating the theoretical displacement at the output end to the input force and the micro-clamping force is as follows: ; In the above formula, This represents the theoretical displacement at the output end. Indicates input force. Indicates micro-clamping force, This represents the input force-output displacement coupling coefficient. This represents the force-displacement compliance coefficient at the output end.

[0015] Furthermore, the correction coefficient Through dimensionless factors It is determined that the dimensionless factor The structure is constructed using the structural parameters of a single-force input, single-stage compliant orthogonal displacement amplification mechanism, and the correction coefficient is... The expression for the dimensionless factor, obtained through finite element simulation data and numerical fitting methods, is as follows: ; In the above formula, Indicates a dimensionless factor. Indicates a compliant hinge Length, This represents the length of the beam with a moderate cross-section in the first flexible beam. Indicates the thickness of a beam with a uniform cross-section. Indicates the minimum thickness of a compliant hinge. This indicates the uniform thickness of the entire compliant mechanism. , , , , This represents the weighting coefficient.

[0016] Furthermore, the expression for the semi-analytical model used for indirect measurement of micro-clamping force is as follows: ; In the above formula, Indicates micro-clamping force, This represents the actual displacement at the output of the single-force input, single-stage compliant orthogonal displacement amplification mechanism. This represents the feature point displacement to output displacement conversion coefficient. This represents the input force-output displacement coupling coefficient. This represents the force-displacement compliance coefficient at the output end. Indicates input force.

[0017] The beneficial effects of the system and measurement method of this invention are as follows: This invention acquires the input force through a force sensor arranged at the input end of the actuator, and simultaneously acquires the actual displacement of point B at the output end of the mechanism along the output direction through a microscopic vision measurement system. The input force and output displacement are used as input quantities, which are substituted into a pre-established semi-analytical model by the data processing module to obtain the corresponding micro-clamping force, thus achieving indirect measurement of the micro-clamping force. This enables non-invasive measurement of the micro-clamping force without the need for additional force measurement structures, avoiding the impact on the original flexibility distribution and force transmission path of the mechanism, and improving measurement accuracy and system stability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an indirect micro-clamping force measurement system according to the present invention; Figure 2 This is a structural block diagram of the micro-clamping force indirect measurement method of the micro-clamping force indirect measurement system of the present invention; Figure 3 This is a partially enlarged structural schematic diagram of the micro-clamping force indirect measurement system provided in a specific embodiment of the present invention; Figure 4 This is a schematic diagram of the motion of a single-force input, single-stage compliant orthogonal displacement amplification mechanism provided in a specific embodiment of the present invention; Figure 5 This is a schematic diagram of the mechanical model of a single-force input, single-stage compliant orthogonal displacement amplification mechanism provided in a specific embodiment of the present invention; Figure 6 This is a schematic diagram of the boundary condition settings for finite element simulation provided in a specific embodiment of the present invention; Figure 7 This is a finite element simulation result and a corresponding simulation deformation diagram of the mechanism provided in a specific embodiment of the present invention; Figure 8 This is a schematic diagram of the finite element simulation verification results of the indirect measurement of micro-clamping force provided in a specific embodiment of the present invention.

[0019] Reference numerals: 1. CCD camera; 2. Camera lens; 3. Camera bracket; 4. Single-force input single-stage compliant orthogonal displacement amplification mechanism; 410. Fixing bolt; 420. Input end; 430. Variable cross-section beam; 440. Output end; 450. Straight beam; 460. Jaw; 5. Piezoelectric actuator; 6. Force sensor; 610. Piezoelectric force sensor; 620. Pre-tightening device; 7. Mechanism fixing base; 8. Three-degree-of-freedom adjustment platform; 9. Connecting base; 10. Vibration isolation table. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0021] Reference Figure 1 This invention provides a micro-clamping force indirect measurement system, including a drive system, a force sensor 6, a single-force input single-stage compliant orthogonal displacement amplification mechanism 4, a microscopic vision measurement system, a data acquisition module, and a data processing module. The force sensor is arranged at the input end of the single-force input single-stage compliant orthogonal displacement amplification mechanism. The drive system is positioned opposite the single-force input single-stage compliant orthogonal displacement amplification mechanism. The microscopic vision measurement system is located at the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism. The data acquisition module is electrically connected to the force sensor. The data processing module is signal-connected to both the microscopic vision measurement system and the data acquisition module. The drive system includes a piezoelectric actuator 5, which is used to apply an input force to a single-force input single-stage compliant orthogonal displacement amplification mechanism; The force sensor is used to detect the input force; The single-force input single-stage compliant orthogonal displacement amplification mechanism is used to generate corresponding orthogonal displacements based on the input force and to form a micro-clamping force; The microscopic visual measurement system includes a CCD camera 1 and a camera lens 2, which are used to acquire image information from the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism. The data acquisition module is used to acquire signals of input force. The data processing module is used to calculate the actual displacement based on the image information of the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism, and to obtain the micro-clamping force based on the input force and the actual displacement.

[0022] In this embodiment, the micro-clamping force indirect measurement method is implemented based on a micro-clamping force indirect measurement system. The micro-clamping force indirect measurement system includes a drive system, a force sensor arranged at the input end of the drive, a single-force input single-stage compliant orthogonal displacement amplification mechanism, a microscopic vision measurement system, a data acquisition module, and a data processing module. The single-force input single-stage compliant orthogonal displacement amplification mechanism includes an input end 420, a variable cross-section beam 430, an output end 440, a straight beam 450, and a jaw 460. The drive system applies an input force to the mechanism through the input end. The mechanism transmits and converts the force and displacement applied by the drive system, causing an orthogonal displacement at the output end and forming a micro-clamping force at the jaw.

[0023] Furthermore, the driving system includes a piezoelectric actuator, and the microscopic vision measurement system includes a CCD camera and a camera lens; the piezoelectric actuator is positioned opposite to the input end of the single-force input single-stage compliant orthogonal displacement amplification mechanism, and is used to apply an input force to the input end of the mechanism; the force sensor is positioned between the piezoelectric actuator and the input end of the mechanism, and is used to detect the input force; the CCD camera and camera lens are positioned facing the output end B of the mechanism, and are used to acquire image information of the B point; the data acquisition module is connected to the force sensor, and is used to acquire the input force signal, wherein the force sensor can be a piezoelectric force sensor 610; the data processing module is connected to the data acquisition module and the microscopic vision measurement system respectively, and is used to calculate the actual displacement based on the image information of the B point, and substitute the input force and the actual displacement into the semi-analytical model to obtain the micro-clamping force.

[0024] The micro-clamping force indirect measurement system also includes a vibration isolation table 10, a three-degree-of-freedom adjustment platform 8, a connecting base 9, a camera bracket 3, a mechanism fixing base 7, and a pre-tightening device 620. The connecting base is fixedly connected to the vibration isolation table, the three-degree-of-freedom adjustment platform is disposed on the connecting base, the mechanism base is disposed on the three-degree-of-freedom adjustment platform, the single-force input single-stage compliant orthogonal displacement amplification mechanism is disposed on the mechanism base by fixing bolts 410, the camera bracket is disposed on the vibration isolation table, the CCD camera and camera lens are mounted on the camera bracket, and the piezoelectric actuator is disposed on the mechanism base by the pre-tightening device. The pre-tightening device is disposed on the mechanism base and cooperates with the force sensor so that the force sensor is located between the piezoelectric actuator and the mechanism input end.

[0025] Reference Figure 2 A method for indirectly measuring the micro-clamping force in a micro-clamping force indirect measurement system, comprising: S100. Based on the preset beam size parameter design equation, determine the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism, and construct a coupling relationship model between the input force, the output displacement and the micro-clamping force. In this embodiment, the single-force input single-stage compliant orthogonal displacement amplification mechanism is designed using design equations. The design process is as follows: several preset dimensional parameters are determined in advance based on the structural layout requirements and dimensional constraints of the target mechanism, and the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism are determined using design equations based on the preset dimensional parameters. The single-force input single-stage compliant orthogonal displacement amplification mechanism is a symmetrical mechanism based on the triangular amplification principle, with a uniform thickness h, and is composed of a flexible beam AB (first flexible beam) with pre-designed dimensional parameters (composed of compliant hinge a, compliant hinge b, and a beam with a uniform cross-section, including preset parameters). Input rigid beam and output rigid body (including preset parameters) , The flexible beam CD, consisting of the second flexible beam with undetermined dimensional parameters, is composed of (including undetermined parameters:) and (the second flexible beam). The flexible beam AB connects the input rigid beam and the output rigid body, and the flexible beam CD connects the output rigid body and the frame. The symmetrical design constitutes a single-force input, single-stage compliant orthogonal displacement amplification compliant mechanism. The design equation for the undetermined beam dimensions is: ; In the above formula, It is the flexibility coefficient of beam CD. According to Castiglione's second theorem, The function is expressed as u, and the parameters are... yes The function of . Similarly, the flexibility coefficient of beam AB. S It can also be expressed in the same way, where the parameters , yes S The function. This represents the characteristic length parameter of the rigid beam at the input end. Indicates the connection point between the first flexible beam and the rigid body at the output end. rigid body center of mass at the output end The characteristic distance.

[0026] In addition, it should be noted that the coupling relationship model is based on the static equilibrium equation, the deformation compatibility equation, the load distribution method for statically indeterminate structures, and Castiglione's second theorem.

[0027] S200. Based on the coupling relationship model, the analytical model between the theoretical displacement of the output end and the input force and micro-clamping force is derived. In this embodiment, the theoretical displacement at the output end Input force With micro-clamping force The following relationship must be satisfied: ; in, and These are coefficients related to the mechanism's geometric and material parameters.

[0028] S300. Perform finite element error analysis on the analytical model to obtain the relationship between the analytical model and the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism. Then, use the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism to construct a dimensionless factor and determine the correction coefficient, and build a semi-analytical model for indirect measurement of micro clamping force. In this embodiment, the correction coefficient is used to characterize the difference between the theoretical displacement and the actual displacement at the output end, and the actual displacement at the output end... Theoretical displacement of the output terminal The following relationship must be satisfied: ; in, The correction coefficient is denoted as .

[0029] Among them, the correction coefficient From dimensionless factor It is determined that the dimensionless factor Constructed from the mechanism's geometric parameters, and the correction coefficients The dimensionless factor was obtained through finite element simulation data and numerical fitting methods. The dimensionless factor is as follows: ; In the above formula, Indicates a dimensionless factor. Indicates a compliant hinge Length, This represents the length of the beam with a moderate cross-section in the first flexible beam. Indicates the thickness of a beam with a uniform cross-section. Indicates the minimum thickness of a compliant hinge. This indicates the uniform thickness of the entire compliant mechanism. , , , , This represents the weighting coefficient.

[0030] Correction coefficient It satisfies the following relationship with the dimensionless factor: ; in, , For about the aspect ratio The function. and The dimensional parameters of the variable cross-section beam in the single-force input single-stage compliant orthogonal displacement amplification mechanism are given. Let the length-to-diameter ratio be... , , about The relationship is as follows: ; The semi-analytical model satisfies: ; In the above formula, Indicates micro-clamping force, This represents the actual displacement at the output of the single-force input, single-stage compliant orthogonal displacement amplification mechanism. This represents the feature point displacement to output displacement conversion coefficient. This represents the input force-output displacement coupling coefficient. This represents the force-displacement compliance coefficient at the output end. Indicates input force.

[0031] S400: Obtain the input force information and input the input force information to the single-force input single-stage compliant orthogonal displacement amplification mechanism to obtain the actual displacement at the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism; In this embodiment, the input force is acquired by a force sensor arranged at the input end of the driver. The force signal output by the force sensor is acquired by the data acquisition module and transmitted to the data processing module. The actual displacement is the displacement of point B at the output end of the mechanism along the output direction. The data processing module performs displacement calculation on the image of point B based on image processing methods.

[0032] The image processing methods include one or more of template matching, feature point tracking, edge recognition, and subpixel localization.

[0033] S500: Input the force information and actual displacement into the semi-analytical model for indirect measurement of micro-clamping force and solve it to obtain the micro-clamping force.

[0034] In this embodiment, the micro-clamping force The specific calculation expression is as follows: ; In the above formula, This represents the theoretical displacement at the output end. Indicates input force. Indicates micro-clamping force, This represents the input force-output displacement coupling coefficient. This represents the force-displacement compliance coefficient at the output end.

[0035] In actual operation, the drive system applies an input force to the input end of the single-stage compliant orthogonal displacement amplification mechanism. Under the action of this input force, the mechanism undergoes elastic deformation, causing displacement at the output end and generating a micro-clamping reaction force at the jaws. Due to the structural characteristics of the mechanism, there is a coupling relationship between the output end displacement and the micro-clamping force.

[0036] During the measurement process, the input force is acquired by a force sensor located at the input end of the actuator, while the actual displacement of point B at the output end of the mechanism along the output direction is acquired by a microscopic vision measurement system. The input force and output displacement are used as input quantities, which are substituted into a pre-established semi-analytical model by the data processing module to obtain the corresponding micro-clamping force, thus achieving indirect measurement of the micro-clamping force. Through this method, this embodiment of the invention achieves non-invasive measurement of the micro-clamping force without the need for additional force measurement structures, avoiding any impact on the original flexibility distribution and force transmission path of the mechanism, and improving measurement accuracy and system stability.

[0037] Therefore, this embodiment of the invention first establishes a coupling relationship model between the input force, the output displacement, and the micro-clamping force based on the structural characteristics of the single-force input single-stage compliant orthogonal displacement amplification mechanism. Further, based on the coupling relationship model, an analytical expression is derived between the theoretical output displacement and the input force and micro-clamping force. Then, finite element error analysis is performed on the analytical expression to obtain the correspondence between the analytical model error and the mechanism's structural parameters. A dimensionless factor is constructed using the mechanism's geometric parameters, and correction coefficients are determined to establish a semi-analytical model for indirect measurement of the micro-clamping force. Further, a force sensor located at the input end of the actuator acquires the input force information, which is then transmitted to the data processing module via a data acquisition module. A microscopic vision measurement system acquires the image information of point B at the mechanism's output end. The data processing module calculates the actual displacement of point B along the output direction based on the image information. Finally, the data processing module substitutes the input force and the actual displacement into the semi-analytical model to obtain the micro-clamping force. This method achieves indirect measurement of the micro-clamping force using the input force and the output displacement without setting up an additional force measuring structure.

[0038] In summary, the micro-clamping force indirect measurement method of this invention is implemented based on a micro-clamping force indirect measurement system. The micro-clamping force indirect measurement system includes a drive system, a force sensor arranged at the input end of the driver, a single-force input single-stage compliant orthogonal displacement amplification mechanism, a microscopic vision measurement system, a data acquisition module, and a data processing module. The single-force input single-stage compliant orthogonal displacement amplification mechanism includes an input end, a variable cross-section beam, an output end, a straight beam, and a jaw. To address the challenges of sensor integration, the potential for additional force-measuring structures to disrupt the original mechanical properties of compliant mechanisms, and the insufficient accuracy of purely analytical models in existing micro-clamping force measurements, this invention establishes a coupling relationship model between input force, output displacement, and micro-clamping force based on the structural characteristics of the mechanism. It derives analytical expressions for the theoretical output displacement, input force, and micro-clamping force. Furthermore, it obtains the relationship between analytical model errors and structural parameters through finite element analysis, introducing dimensionless factors and correction coefficients constructed from the mechanism's geometric dimensions to build a semi-analytical model. The input force is then acquired by a force sensor, and the actual displacement of point B at the mechanism's output end along the output direction is obtained by a microscopic vision measurement system. Substituting the input force and the actual displacement into the semi-analytical model yields the micro-clamping force. This invention eliminates the need for additional force-measuring structures, does not alter the original flexibility distribution or force transmission path of the mechanism, and offers advantages such as high measurement accuracy, non-invasiveness, suitability for miniaturized systems, and applicability as a constant force control feedback signal.

[0039] This invention combines mechanical modeling methods with finite element error correction methods, enabling the established semi-analytical model to take into account both the physical interpretability of analytical models and the high precision characteristics of numerical models. This avoids the influence of additional force measuring structures on the flexibility distribution and force transmission path of the mechanism in traditional direct measurement methods, while overcoming the problems of weak applicability and insufficient accuracy of purely empirical models.

[0040] Finally, the embodiments of the present invention will be explained and described in conjunction with the accompanying drawings: like Figure 3 As shown, the micro-clamping force indirect measurement system of this embodiment includes a driving system, a force sensor arranged at the input end of the driver, a single-force input single-stage compliant orthogonal displacement amplification mechanism, a microscopic vision measurement system, a data acquisition module, and a data processing module. The driving system is used to provide driving force to the input end of the mechanism; the force sensor is used to acquire input force information; the microscopic vision measurement system is used to acquire the image of point B at the output end of the mechanism; the data acquisition module is used to acquire the force signal output by the force sensor; the data processing module is used to perform displacement calculation at point B, and substitute the input force and displacement into the micro-clamping force indirect measurement model to obtain the micro-clamping force.

[0041] The drive system may employ a piezoelectric actuator, and the microscopic vision measurement system may include a CCD camera and a camera lens. The micro-clamping force indirect measurement system may further include a vibration isolation table, a three-degree-of-freedom adjustment platform, a connecting base, a camera bracket, a mechanism base, and a pre-tightening device. The connecting base is mounted on the vibration isolation table, the three-degree-of-freedom adjustment platform is mounted on the connecting base, the mechanism base is mounted on the three-degree-of-freedom adjustment platform, the single-force input single-stage compliant orthogonal displacement amplification mechanism is mounted on the mechanism base, the camera bracket is mounted on the vibration isolation table, the CCD camera and camera lens are mounted on the camera bracket, and the pre-tightening device is mounted on the mechanism base to cooperate with the piezoelectric actuator and force sensor to achieve input force loading and detection.

[0042] The experimental base, mounting bracket, and platform components are used to fix, position, and install the various parts, ensuring the stability of the measurement system during operation. The microscopic vision measurement system may include a camera, lens, and imaging support structure, its main function being to acquire image information at point B at the mechanism's output end. The data processing module can be implemented using host computer software; in one embodiment, MATLAB can be used, for example, to calculate the displacement at point B and solve for the micro-clamping force. Together, the system constitutes a complete framework for input force acquisition, output displacement acquisition, and inverse calculation of the micro-clamping force model.

[0043] like Figure 4 As shown, the single-force input single-stage compliant orthogonal displacement amplification mechanism includes an input end, a variable cross-section beam, an output end, a straight beam, and a jaw. In one embodiment, the mechanism can also be divided into a flexible beam AB, a flexible beam CD, an input end rigid beam, and an output end rigid body from a structural design perspective. The flexible beam AB and the flexible beam CD are respectively connected between the input end rigid beam and the output end rigid body, forming the compliant force transmission structure of the mechanism. After the drive system applies an input force to the input end, the input force is transmitted to the flexible beam AB and the flexible beam CD via the input end rigid beam. The elastic deformation of the flexible beam enables the transmission and conversion of force and displacement, resulting in orthogonal displacement at the output end and forming a micro-clamping force at the jaw.

[0044] The single-force input, single-stage compliant orthogonal displacement amplification mechanism features single-force input, single-stage displacement amplification, and orthogonal displacement transmission. The displacement of point B at its output end along the output direction characterizes the mechanism's output response under the combined action of the input force and the micro-clamping reaction force. Therefore, the micro-clamping force can be indirectly obtained by measuring the input force and the displacement of point B at the output end, combined with the mechanism's mechanical model.

[0045] The single-force input, single-stage compliant orthogonal displacement amplification mechanism is designed using design equations. During the design process, several preset dimensional parameters are first determined based on the target mechanism's structural layout space and machining size limitations. Then, these preset dimensional parameters are substituted into the design equations to obtain the undetermined structural parameters of the single-force input, single-stage compliant orthogonal displacement amplification mechanism, thereby completing the structural design of the mechanism.

[0046] The single-force input, single-stage compliant orthogonal displacement amplification mechanism includes a flexible beam AB with known dimensional parameters, a flexible beam CD with undetermined dimensional parameters, an input-end rigid beam, and an output-end rigid body. The flexible beams AB and CD are respectively connected between the input-end rigid beam and the output-end rigid body, forming the single-force input, single-stage compliant orthogonal displacement amplification mechanism.

[0047] Furthermore, during the design process, the dimensional parameters of the flexible beam AB can be used as known conditions, and the dimensional parameters of the flexible beam CD can be used as parameters to be determined. Combined with the overall structural layout and performance requirements of the mechanism, the dimensional parameters of the flexible beam CD can be determined through the design equations. Using the above design method, the undetermined beam dimensional parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism can be determined under the premise of satisfying structural dimensional constraints, providing a structural foundation for establishing the coupling relationship model between the input force, output displacement, and micro-clamping force. The preset dimensional parameters include material parameters and the geometric dimensional parameters of known components in the mechanism. Specifically, as shown in Table 1, the preset structural parameters used in the simulation example for designing the single-force input single-stage compliant orthogonal displacement amplification mechanism are given, wherein the material selected is aluminum alloy. , , , , , and These are the preset input parameters in the design equations. These parameters characterize the initial constraints of the known flexible beam AB, the input rigid beam, the output rigid body, and the overall structural arrangement of the mechanism.

[0048] Table 1. Preset structural parameters for simulation examples ; Substituting the preset structural parameters shown in Table 1 into the design equation, the dimensional parameters of the undetermined flexible beam CD in the mechanism can be obtained, and the structural design of the single-force input single-stage compliant orthogonal displacement amplification mechanism can be completed. As shown in Table 2, the design results obtained based on the design equation are given, namely, the determined values ​​of the undetermined flexible beam CD and related structural parameters.

[0049] Table 2 Design Results ; like Figure 5 As shown, in order to establish the relationship model between the input force, output displacement and micro-clamping force of the mechanism, the static equilibrium equation, deformation compatibility equation, load distribution method of statically indeterminate structure and Castiglione's second theorem are used for modeling based on the structural characteristics of the mechanism.

[0050] The mechanism can be simplified to a half-side model for analysis based on its geometric symmetry. By performing force analysis on key sections, the input force can be established. Theoretical displacement at the output end and micro-clamping force The coupling relationship between them. Further, the following analytical expression can be obtained: ; in, and These are coefficients related to the geometric and material parameters of the mechanism.

[0051] From the above analytical expression, we can further obtain the analytical expression for the micro-clamping force: ; Because the analytical model employs idealized assumptions during its development, a certain error exists between the analytical results and the actual structural response. To improve the accuracy of indirect measurement of micro-clamping force, finite element error analysis is performed on the analytical model.

[0052] Specifically, finite element simulations were performed on a single-force input, single-stage compliant orthogonal displacement amplification mechanism under different structural parameters to obtain the actual output response, which was then compared with the predicted value of the analytical model. This yielded the correspondence between the analytical model error and the structural parameters of the mechanism.

[0053] Based on this, a correction factor is introduced. This is used to characterize the difference between the theoretical displacement and the actual displacement at the output end, so that the actual displacement at the output end... Theoretical displacement at the output end The following relationship must be satisfied: ; Furthermore, a dimensionless factor constructed from the mechanism's geometric parameters is introduced. The dimensionless factor can be composed of at least one or more of the following: the ratio of flexible beam length to thickness, the ratio of flexible beam thickness to mechanism characteristic dimension, and the ratio of flexible beam spacing to mechanism characteristic dimension. The correction coefficient... From dimensionless factor The determination was made and obtained through finite element simulation data and numerical fitting methods.

[0054] This allows for the establishment of a semi-analytical model for the indirect measurement of micro-clamping forces: ; Through the above modifications, the analytical model can be better aligned with the actual structural response, thereby improving the accuracy of indirect measurement of micro-clamping force. The semi-analytical model can be pre-established and loaded by the data processing module before measurement, and directly invoked during the measurement process based on the input force and actual displacement.

[0055] In this embodiment, the input force is acquired by a force sensor located at the input end of the actuator. The force signal output by the force sensor is acquired by a data acquisition module and transmitted to the data processing module. Simultaneously, a microscopic vision measurement system acquires an image of point B at the output end of the mechanism. The data processing module performs displacement calculations on the image of point B based on an image processing method to obtain the actual displacement of point B along the output direction. The image processing method may include one or more of template matching, feature point tracking, edge recognition, and sub-pixel localization. The image processing method can be implemented using existing mature methods; the innovation of this invention lies in the indirect measurement model of micro-clamping force based on the input force and output displacement, and its application.

[0056] In practical applications, the semi-analytical model can be pre-established offline through a combination of theoretical modeling and finite element analysis, and then directly invoked during the measurement process.

[0057] Specifically, before measurement, a corresponding coupling relationship model is established based on the geometric parameters of the target mechanism, and the relationship between the correction coefficient and the dimensionless factor is determined through finite element analysis, thereby constructing the semi-analytical model. Once the semi-analytical model is established, finite element analysis does not need to be repeated during the actual measurement process.

[0058] During the measurement phase, it is only necessary to obtain the input force and the actual displacement of the output point B, and substitute them into the semi-analytical model to quickly obtain the micro-clamping force, thereby realizing the real-time or near-real-time measurement of the micro-clamping force.

[0059] Furthermore, to verify the accuracy of the established micro-clamping force indirect measurement model, the single-force input single-stage compliant orthogonal displacement amplification mechanism was verified and analyzed based on the finite element simulation method.

[0060] In the finite element model, a known input force is applied to the input terminal of the actuator. A known micro-clamping force is applied at the output end of the mechanism. As a contact load, the horizontal displacement of point B at the output end of the mechanism along the output direction was calculated. .

[0061] The input force and the actual displacement of the output obtained by simulation Substituting into the semi-analytical model, the corresponding micro-clamping force can be obtained by inverse calculation. .

[0062] By comparing the micro-clamping forces applied in finite element simulations The micro-clamping force obtained by inverse calculation using the semi-analytical model The relative error between the two is calculated to evaluate the prediction accuracy of the model.

[0063] Simulation results show that the micro-clamping force obtained by the semi-analytical model inverse calculation has good consistency with the finite element simulation results, verifying the effectiveness of the indirect measurement method of micro-clamping force. Specifically, as follows... Figure 6 , Figure 7 as well as Figure 8 The image shows a description of how to verify the effectiveness of this method using finite element simulation. Figure 6 This refers to the boundary condition settings for finite element methods. Figure 7 This is a simulation diagram of the displacement at point B using finite element analysis. Figure 8 The results show the comparison between simulation verification and theoretical calculations of the proposed measurement method under five different load conditions.

[0064] The content of the above method embodiments is applicable to this system embodiment. The specific functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0065] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this is not intended to limit the scope of the embodiments of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the embodiments of the present application.

Claims

1. A micro-clamping force indirect measurement system, characterized in that, The system includes a drive system, a force sensor, a single-force-input single-stage compliant orthogonal displacement amplification mechanism, a microscopic vision measurement system, a data acquisition module, and a data processing module. The force sensor is positioned at the input end of the single-force-input single-stage compliant orthogonal displacement amplification mechanism. The drive system is positioned opposite the single-force-input single-stage compliant orthogonal displacement amplification mechanism. The microscopic vision measurement system is positioned at the output end of the single-force-input single-stage compliant orthogonal displacement amplification mechanism. The data acquisition module is electrically connected to the force sensor. The data processing module is connected to both the microscopic vision measurement system and the data acquisition module via signal connections. The drive system includes a piezoelectric actuator for applying an input force to a single-force input single-stage compliant orthogonal displacement amplification mechanism; The force sensor is used to detect the input force; The single-force input single-stage compliant orthogonal displacement amplification mechanism is used to generate corresponding orthogonal displacements based on the input force and to form a micro-clamping force; The microscopic visual measurement system includes a CCD camera and a camera lens, used to acquire image information from the output end of a single-force input single-stage compliant orthogonal displacement amplification mechanism; The data acquisition module is used to acquire signals of input force. The data processing module is used to calculate the actual displacement based on the image information of the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism, and to obtain the micro-clamping force based on the input force and the actual displacement.

2. The micro-clamping force indirect measurement system according to claim 1, characterized in that, The single-force input single-stage compliant orthogonal displacement amplification mechanism is a symmetrical mechanism based on the triangular amplification principle. Specifically, it includes a first flexible beam, a second flexible beam, an input end rigid body beam, an output end rigid body, and a jaw. The first flexible beam and the second flexible beam are respectively connected between the input end rigid body beam and the output end rigid body, forming the compliant force transmission structure of the mechanism. After the drive system applies an input force to the input end, the input force is transmitted to the first and second flexible beams through the input end rigid body beam. The transmission and conversion of force and displacement are realized through the elastic deformation of the flexible beams, causing the output end rigid body to generate orthogonal displacement and forming a micro-clamping force at the jaw.

3. The micro-clamping force indirect measurement system according to claim 2, characterized in that, The micro-clamping force indirect measurement system further includes a vibration isolation table, a three-degree-of-freedom adjustment platform, a connecting base, a camera bracket, a mechanism base, and a pre-tightening device. The connecting base is fixedly connected to the vibration isolation table, the three-degree-of-freedom adjustment platform is disposed on the connecting base, the mechanism base is disposed on the three-degree-of-freedom adjustment platform, the single-force input single-stage compliant orthogonal displacement amplification mechanism is disposed on the mechanism base by fixing bolts, the camera bracket is disposed on the vibration isolation table, the CCD camera and camera lens are mounted on the camera bracket, and the piezoelectric actuator is disposed on the mechanism base by the pre-tightening device. The pre-tightening device is disposed on the mechanism base and cooperates with the force sensor so that the force sensor is located between the piezoelectric actuator and the mechanism input end.

4. A method for indirectly measuring the micro-clamping force in a micro-clamping force indirect measurement system, characterized in that, Includes the following steps: Based on the pre-set beam size parameter design equation, the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism are determined, and a coupling relationship model between the input force, the output displacement and the micro-clamping force is constructed. Based on the coupling relationship model, an analytical model is derived to show the relationship between the theoretical displacement at the output end and the input force and micro-clamping force. Finite element error analysis was performed on the analytical model to obtain the relationship between the analytical model and the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism. The dimensionless factor and correction coefficient were constructed using the structural parameters of the single-force input single-stage compliant orthogonal displacement amplification mechanism to build a semi-analytical model for indirect measurement of micro clamping force. Acquire input force information and input the input force information into a single-force input single-stage compliant orthogonal displacement amplification mechanism to obtain the actual displacement at the output end of the single-force input single-stage compliant orthogonal displacement amplification mechanism; The input force information and actual displacement are input into a semi-analytical model for indirect measurement of micro-clamping force to obtain the micro-clamping force.

5. The method for indirect measurement of micro-clamping force in a micro-clamping force indirect measurement system according to claim 4, characterized in that, The expression for the preset beam dimension parameter design equation is as follows: ； In the above formula, Indicates the rigid body at the output end. Orthogonal displacement output direction displacement, Indicates the rigid body at the output end. Displacement in direction, Indicates the rigid body at the output end. Displacement in direction, This represents the theoretical displacement amplification factor of the mechanism. , This represents the torque-to-linear displacement conversion factor of the mechanism. This represents the normalized unit input force applied at the input terminal. This represents the characteristic length parameter of the rigid beam at the input end. Indicates the connection point between the first flexible beam and the rigid body at the output end. rigid body center of mass at the output end The feature distance, This indicates the magnification ratio of the mechanism. , This represents the compliant hinge angle correction factor for the first flexible beam.

6. The method for indirect measurement of micro-clamping force in a micro-clamping force indirect measurement system according to claim 5, characterized in that, The coupling relationship model is established based on the static equilibrium equation, the deformation compatibility equation, the load distribution method for statically indeterminate structures, and Castiglione's second theorem.

7. The method for indirect measurement of micro-clamping force in a micro-clamping force indirect measurement system according to claim 6, characterized in that, The specific expression of the analytical model relating the theoretical displacement at the output end to the input force and the micro-clamping force is shown below: ； In the above formula, This represents the theoretical displacement at the output end. Indicates input force. Indicates micro-clamping force, This represents the input force-output displacement coupling coefficient. This represents the force-displacement compliance coefficient at the output end.

8. The method for indirect measurement of micro-clamping force in a micro-clamping force indirect measurement system according to claim 7, characterized in that, The correction coefficient Through dimensionless factors It is determined that the dimensionless factor The structure is constructed using the structural parameters of a single-force input, single-stage compliant orthogonal displacement amplification mechanism, and the correction coefficient is... The expression for the dimensionless factor, obtained through finite element simulation data and numerical fitting methods, is as follows: ； In the above formula, Indicates a dimensionless factor. Indicates a compliant hinge Length, This represents the length of the beam with a moderate cross-section in the first flexible beam. Indicates the thickness of a beam with a uniform cross-section. Indicates the minimum thickness of a compliant hinge. This indicates the uniform thickness of the entire compliant mechanism. , , , , This represents the weighting coefficient.

9. The method for indirect measurement of micro-clamping force in a micro-clamping force indirect measurement system according to claim 8, characterized in that, The specific expression of the semi-analytical model for indirect measurement of micro-clamping force is as follows: ； In the above formula, Indicates micro-clamping force, This represents the actual displacement at the output of the single-force input, single-stage compliant orthogonal displacement amplification mechanism. This represents the feature point displacement to output displacement conversion coefficient. This represents the input force-output displacement coupling coefficient. This represents the force-displacement compliance coefficient at the output end. Indicates input force.

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