An interactive system and method for measuring skin friction performance

Abstract

The present invention discloses an interactive system and method for measuring the friction performance of skin, wherein the method comprises: collecting skin characteristic indicators; controlling the friction between the test indenter and the skin surface, collecting the image of the skin surface; wherein the skin surface is provided with a speckle mark; obtaining a continuous image deformation field according to the collected image; obtaining the skin force data during the friction between the test indenter and the skin; simplifying two friction models according to the skin characteristic indicators based on a numerical iteration calculation method; establishing a friction force response model based on skin characteristics based on the continuous image deformation field, the skin force data and the two friction models. The present invention combines the real deformation and force data of the skin for simultaneous domain analysis, simplifies the two friction models based on the numerical iteration calculation method, and can establish a friction force response model based on skin characteristics for individual differences and site differences in skin characteristics. The present invention can be widely used in the field of robot interaction.

Description

Technical Field

[0001] The present invention relates to the field of robot interaction, and in particular to an interactive system and method for measuring skin friction performance. Background Art

[0002] With the increasing demand for modern health care, robotic devices for human skin and muscle massage have been widely developed and studied. When robots move and apply force according to a predetermined trajectory, they often ignore the movement resistance caused by the stretching and deformation of human skin during human-machine contact friction, as well as the pain perception of human skin, and even cause skin damage. Studies have shown that human skin has complex skin mechanical properties, and the stress-strain curve of the skin has obvious nonlinearity, anisotropy, and viscoelastic hysteresis. In addition, different friction response curves are presented due to different individuals, skin parts, ages, bone fat and muscle distribution, environmental temperature and humidity, and other conditions.

[0003] At present, the research on human massage robot operation at home and abroad is limited to the compliant control of normal force and position in nonlinear environments such as local perpendicularity to local muscles, and the robot position is corrected by combining the skin normal elastic compensation. These domestic robot control technologies have a certain lag in application, and they complete short-distance loading conditions in fixed-point normal directions, and do not involve robot interaction strategies under friction movement conditions. In actual contact operations, the robot must continuously apply force to the surface muscles of the skin and move frictionally. The surface skin muscles are prone to flexible deformations such as squeezing and stretching: on the one hand, the flexible deformation of the skin brings resistance to the robot movement, which seriously affects the actual trajectory movement of the robot; on the other hand, the human skin is distributed with a large number of nerve tissues that can perceive external stimuli. The flexible deformation of the skin brings pain and discomfort to the operation object, which ultimately affects the human perception of the robot massage operation.

[0004] The friction performance between skin can be quantitatively described by the skin force information and flexible deformation information, which also needs to consider the characteristic indicators of different individual human skin viscoelasticity, skin location, age, etc. Therefore, quantitative analysis and research on the friction performance between human skin based on skin characteristics has important practical application significance. In the optimization planning of robot operations, incorporating sufficient and accurate friction information can effectively carry out personalized planning and safety strategy design, thereby improving the robot's perception of human skin contact feedback.

[0005] Existing technologies cannot ensure that the robot can maintain the comfortable feeling of human skin during the interactive friction process, and therefore cannot improve the robot's perception of real-time feedback from human skin, reduce skin friction damage and human discomfort, and improve operational safety. Summary of the invention

[0006] In order to solve at least one of the technical problems existing in the prior art to a certain extent, the present invention aims to provide an interactive system and method for measuring skin friction performance.

[0007] The technical solution adopted by the present invention is:

[0008] An interactive system for measuring skin friction properties, comprising:

[0009] Robotic arm;

[0010] A test pressure head, fixed at the end of the mechanical arm, for contacting with the skin;

[0011] An industrial camera assembly, used to collect images of the skin when it is in contact with the test indenter; wherein a speckle mark is provided on the surface of the skin;

[0012] A six-dimensional force sensor, disposed at the end of the mechanical arm, for obtaining the friction force generated when the test pressure head contacts the skin;

[0013] The control host side is used to control the moving trajectory of the robotic arm, receive the image information collected by the industrial camera component and the friction information collected by the six-dimensional force sensor, and build a friction response model based on skin characteristics according to the received information.

[0014] Further, the industrial camera assembly includes two CMOS industrial cameras, the two CMOS industrial cameras are arranged at the same horizontal height, and the intersection of the sight lines of the two CMOS industrial cameras falls on the target skin area; the target skin area is an area with a speckle mark;

[0015] and / or,

[0016] The test pressure head is in the shape of a sphere, a hemisphere or a cube.

[0017] Another technical solution adopted by the present invention is:

[0018] An interactive method for measuring skin friction properties comprises the following steps:

[0019] Collect skin characterization indicators;

[0020] Controlling the friction between the test indenter and the skin surface to collect an image of the skin surface; wherein a speckle mark is provided on the skin surface;

[0021] Acquire a continuous image deformation field based on the collected images;

[0022] Acquiring skin force data during the friction between the test indenter and the skin;

[0023] Based on the numerical iteration calculation method, the two-term friction model is simplified according to the skin characterization index;

[0024] A friction force response model based on skin characteristics is established according to the continuous image deformation field, skin force data and two friction models.

[0025] Furthermore, the collecting of skin characteristic indicators includes:

[0026] Move the test indenter to the skin surface, and record the position where the test indenter just contacts the skin without causing deformation as the starting point;

[0027] By controlling the mechanical arm, the test indenter is pressed into the skin to a preset depth in a normal direction;

[0028] Record the normal force-indentation depth curve F n -δ, obtain the elastic modulus E of the skin at that location as a skin characterization index.

[0029] Furthermore, the test indenter is a sphere, and the expression of the skin elastic modulus E is:

[0030]

[0031] Among them, F n represents the normal force, v is the Poisson’s ratio of the skin, δ represents the normal penetration depth of the skin, and R represents the radius of the test indenter.

[0032] Furthermore, the speckle mark is a disordered speckle mark with black dots as elements, and the control test indenter rubs against the skin surface to collect an image of the skin surface, including:

[0033] Controlling the test indenter to rub against the skin surface, so that the dot speckle is displaced as the skin deforms;

[0034] Skin images with circular speckles are continuously acquired, and the brightness and contrast of the continuously acquired images are adjusted, and filtering is performed to obtain speckle images.

[0035] Furthermore, the step of acquiring a continuous image deformation field according to the collected image includes:

[0036] Performing stereo matching processing on the continuous speckle images to obtain a continuous deformation field of the speckle that changes with time;

[0037] A skin stretch value-time curve ΔX-T is obtained according to the speckle continuous deformation field.

[0038] Furthermore, the step of obtaining the skin force data during the friction between the test indenter and the skin includes:

[0039] During the movement of the test head, the force data in the three directions of X, Y and Z are obtained by the six-dimensional force sensor; wherein the force data includes the tangential force-time curve F in the same direction as the movement direction. x -T, and the normal force-time curve F in the same direction as the loading z -T.

[0040] Furthermore, the expression of the two-term friction model is:

[0041]

[0042]

[0043] B=α

[0044]

[0045] In the formula, F total represents the total friction, E is the elastic modulus of the skin, τ 0 is the inherent interface shear strength, α is the pressure coefficient, β is the skin viscosity coefficient, R is the radius of the test indenter, and W is the constant force load;

[0046] Wherein, the load loading interval P = {W 1 ,W 2 ,…,W m}, m is the total number of loading times;

[0047] Based on the numerical iteration method, multiple powers are combined to solve the parameters k and n in the simplified two-term friction model: cyclic calculation loading interval P = {W 1 ,W 2 ,…,W m K = {k 1 ,k 2 ,…,k m} and N = {n 1 ,n 2 ,…,n m}, get the average value

[0048] Furthermore, the friction force response model based on skin characteristics is established according to the continuous image deformation field, the skin force data and the two friction models, including:

[0049] Combining the skin stretch value-time curve ΔX-T and force data F x -T, F z -T performs simultaneous domain analysis, fuses the skin characteristic index and the two friction models, and establishes a friction force response model based on skin characteristics kW n ∝ΔX.

[0050] The beneficial effects of the present invention are as follows: the present invention combines the real deformation and force data of the skin for simultaneous domain analysis, simplifies the two friction models based on the numerical iteration calculation method, and can establish a friction force response model based on skin characteristics for individual differences and site differences in skin characteristics, providing reference information for robot characterization operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0052] Figure 1 is a schematic structural diagram of an interactive system for measuring skin friction performance in an embodiment of the present invention;

[0053] Figure 2 is a schematic diagram of a continuous deformation field of skin speckle in an embodiment of the present invention;

[0054] Figure 3 It is a flowchart of the steps of an interactive method for measuring skin friction performance in an embodiment of the present invention.

[0055] Figure 1 The figure marks in the figure: 1-mechanical arm, 2-control host end, 3-test pressure head, 4-six-dimensional force sensor, 5-industrial camera component, 6-skin, 7-speckle mark. DETAILED DESCRIPTION

[0056] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0057] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0058] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0059] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0060] Glossary:

[0061] Two-term friction model: The two-term friction model is composed of two components: adhesion friction and deformation friction. The total friction force F total It can be expressed as: F total =F adhesion +F deformation , where the adhesive friction component F adhesion It is defined as the interfacial shear resistance caused by the formation and fracture of the atomic connectors between the two materials at the contact interface, that is, the transient interaction of the van der Waals forces within the contact surface. deformation It is defined as the energy lost due to the viscoelastic deformation of the spherical indenter and the flexible material of the skin and not fully recovered. The two components of the two-term friction model can be expanded as:

[0062]

[0063]

[0064] Where E is the elastic modulus of the skin, τ 0 is the inherent interfacial shear strength, α is the pressure coefficient, β is the skin viscosity coefficient, R is the radius of the test indenter, W is the constant force load, and v is the Poisson's ratio of the skin.

[0065] like Figure 1 As shown, this embodiment provides an interactive system for measuring skin friction performance, including:

[0066] Robotic arm 1;

[0067] A test indenter 3, with a gripper fixed at the end of the mechanical arm 1, for contacting the skin 6;

[0068] An industrial camera assembly 5, used to collect images of the skin 6 when it is in contact with the test indenter; wherein a speckle mark 7 is provided on the surface of the skin 6;

[0069] A six-dimensional force sensor 4 is provided at the end of the mechanical arm 1 and is used to record the friction force generated when the test pressure head 3 contacts the skin 6;

[0070] The control host terminal 2 is used to control the moving trajectory of the robot arm 1, receive the image information collected by the industrial camera component 5 and the friction information collected by the six-dimensional force sensor, and build a friction response model based on skin characteristics according to the received information.

[0071] As an optional embodiment, the industrial camera assembly 5 includes but is not limited to two CMOS industrial cameras; the two CMOS industrial cameras are set at the same level, and the intersection of the sight lines of the two CMOS industrial cameras falls on the target skin area; the target skin area is an area with a speckle mark, such as Figure 2 shown.

[0072] As an optional implementation, the shape of the test indenter 3 includes but is not limited to a sphere, a hemisphere, and a cube.

[0073] Based on the above interactive system, such as Figure 3 As shown, this embodiment provides an interactive method for measuring skin friction performance. According to individual skin characteristic indicators, a friction model is established as real-time feedback information to improve the robot's perception of human contact and improve the safety and human comfort of the human-machine interactive friction process. The method specifically includes the following steps:

[0074] S1. Collect skin characteristic indicators.

[0075] In this embodiment, the test indenter is a sphere with a diameter of 20 mm and made of 304 stainless steel with a smooth surface. The smooth and flat skin on the inner side of the forearm of the test subject is selected. The robot is started to move the test indenter to the surface. The position where the test indenter just touches the skin without deformation is taken as the starting point. The normal pressure is pressed into the specified depth of 5 mm. The six-dimensional sensor records the normal force-indentation depth curve F z -δ.

[0076]

[0077] As an optional implementation, in order to obtain the elastic modulus value of the skin at that location, the elastic modulus of the skin at multiple locations on the path is repeatedly tested according to the robot interactive friction path, and the average equivalent elastic modulus E is calculated. * .

[0078] S2. Control the test indenter to rub against the skin surface and collect an image of the skin surface; wherein a speckle mark is provided on the skin surface.

[0079] In this embodiment, if Figure 2 As shown, the printed speckle sticker is a disordered speckle marking sticker with black dots with a diameter of 3 mm as elements, which is printed on the target skin area by water transfer printing. The two industrial cameras are placed at the same horizontal height, and the intersection of the camera's line of sight should fall on the target skin area.

[0080] Specifically, when the test indenter rubs against the skin surface, the speckle dots move with the deformation of the skin, and the camera synchronously collects continuous images at a frequency of ten frames per second. The continuously collected images are adjusted in brightness and contrast and filtered to obtain clear speckle images.

[0081] S3. Acquire a continuous image deformation field according to the collected image.

[0082] In this embodiment, a digital image correlation algorithm is used to perform stereo matching processing on the continuous images of skin speckles. The conversion matrix between the imaging pixel coordinates and the spatial position coordinates of the two industrial cameras is calculated by the calibration algorithm. The continuous processed images before and after deformation are calculated according to the conversion matrix to obtain the spatial position coordinates of the marking points corresponding to the skin speckle area. The position coordinates of the marking points of the original skin speckle area before deformation are used as a relative reference. Finally, Figure 2 The continuous deformation field of speckle that changes with time is shown, which contains relative displacement data in three directions: X, Y, and Z. Specifically, the skin stretch value-time curve ΔX-T is obtained, and any point in the skin speckle area marking point is selected. The relative displacement data of the point in the X direction that changes with time is the skin stretch value-time curve ΔX-T at the marking point, and the maximum relative displacement value on the curve is recorded as the maximum skin stretch value ΔX at the marking point. maximum .

[0083] S4. Obtaining skin force data during the friction between the test indenter and the skin.

[0084] Record the skin force data during the friction of the test indenter, read all the data of the six-dimensional force position sensor installed at the end of the robot, and obtain the tangential force-time curve F in the same direction as the movement x -T, normal force time curve F in the same direction as loading z -T.

[0085] Specifically, according to the friction stage law of the contact interface, the maximum adhesive friction force F when the friction force curve rises from the beginning of sliding to the maximum is obtained: static , maximum adhesive friction F static The corresponding sliding time node T 0 , the average sliding friction F from the maximum adhesive friction to the moment of sliding stop dynamic :

[0086]

[0087] S5. Based on the numerical iteration calculation method, the two-item friction model is simplified according to the skin characterization indicators.

[0088] In this embodiment, a simplified two-term friction model is proposed, and the total friction force is described as F total =kW n .

[0089] According to skin characterization indicators: skin elastic modulus E, inherent interface shear strength τ 0 , pressure coefficient α, skin viscosity coefficient β, test head radius R, constant force load W, the loading range is P = {W 1 ,W 2 ,…,W m}. m is the total number of loadings. Solve for the two friction model parameters A, B, and C.

[0090]

[0091] B=α

[0092]

[0093] Specifically, in the load loading interval P = {W 1 ,W 2 ,…,W m}, m is the total number of loads, satisfying Based on the numerical iteration method, multiple powers are combined to solve the parameters k and n in the simplified two-term friction model: cyclic calculation loading interval W = {W 1 ,W 2 ,…,W m K = {k 1 ,k 2 ,…,k m} and N = {n 1 ,n 2 ,…,n m Specifically, get the average

[0094] Specifically, under different constant force loading friction operations, the friction force response power function F is obtained. total =kW n . Maximum adhesive friction F static and the average sliding friction F dynamic The characteristic parameter k can be solved by the calculation method based on numerical iteration static 、n static , k dynamic 、n dynamic . Obtain the corresponding friction force response power function

[0095] S6. A friction force response model based on skin characteristics is established according to the continuous image deformation field, skin force data and two friction models.

[0096] Finally, combining the continuous deformation field data ΔX-T and the force data F x -T, F static -T etc. are integrated in the same domain. For the skin characteristic index and the friction response power function, the skin is considered to be an incompressible elastic material. Nonlinear fitting is performed using fitting methods including but not limited to the least square method to establish a friction response model based on skin characteristics, that is, the force-deformation relationship F x -ΔX、F static -ΔX maximum , and its nonlinear expressions are F x =S x (ΔX), F static =S static (ΔX maximum ).

[0097] In summary, the present invention has at least the following advantages and beneficial effects compared to the prior art:

[0098] (1) The interactive system proposed in the present invention can accurately measure and analyze the friction performance between objects and human skin in real application scenarios. It solves the difficulties of the current large-scale friction test instruments with limited testing space and single scenes, and can complete the measurement in more complex friction scenes, and conduct friction performance tests on different human bodies, different parts, and different contact conditions, with strong operability.

[0099] (2) The present invention can be applied to basic research scenarios such as contact friction performance testing and contact mechanics modeling of various flexible materials such as silicone, skin, and muscle, and has certain practical value.

[0100] (3) The interactive system proposed in the present invention simplifies the two-term friction model based on the numerical iterative calculation method, simplifies the parameters of the friction response model, and establishes a friction model based on skin feature indicators by combining continuous deformation field data, so as to provide feedback information for the machine to perceive contact with different feature environments.

[0101] The present application also discloses a computer program product or a computer program, which includes a computer instruction stored in a computer-readable storage medium. A processor of a computer device can read the computer instruction from the computer-readable storage medium, and the processor executes the computer instruction, so that the computer device executes Figure 3 The method shown.

[0102] In some selectable embodiments, the function / operation mentioned in the block diagram may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the present invention is provided by way of example, for the purpose of providing a more comprehensive understanding of technology. The disclosed method is not limited to the operation and logic flow presented herein. Selectable embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part for which is described as a larger operation is performed independently.

[0103] In addition, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise specified, one or more of the functions and / or features described may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in separate physical devices or software modules. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the present invention. More specifically, in view of the properties, functions, and internal relationships of the various functional modules in the device disclosed herein, the actual implementation of the module will be understood within the conventional skills of the engineer. Therefore, those skilled in the art can implement the present invention set forth in the claims without excessive experimentation using ordinary techniques. It is also understood that the specific concepts disclosed are merely illustrative and are not intended to limit the scope of the present invention, which is determined by the full scope of the appended claims and their equivalents.

[0104] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0105] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0106] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0107] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0108] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0109] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0110] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

[0111] The present invention is based on a Guangdong Natural Science Foundation project: Research on the friction deformation mechanism of viscoelastic bodies and comfortable and compliant intelligent control under human-machine contact motion.

Claims

1. An interactive method for measuring skin friction properties, characterized in that: The following steps are involved: Collect skin characterization indicators; Controlling the friction between the test indenter and the skin surface to collect an image of the skin surface; wherein a speckle mark is provided on the skin surface; Acquire a continuous image deformation field based on the collected images; Acquiring skin force data during the friction between the test indenter and the skin; Based on the numerical iteration calculation method, the two-term friction model is simplified according to the skin characterization index; A friction force response model based on skin characteristics is established according to the continuous image deformation field, skin force data and two friction models; The collecting of skin characteristic indicators includes: Move the test indenter to the skin surface, and record the position where the test indenter just contacts the skin without causing deformation as the starting point; By controlling the mechanical arm, the test indenter is pressed into the skin to a preset depth in a normal direction; Record the normal force-indentation depth curve F n -δ, obtain the elastic modulus E of the skin at that location as a skin characterization index; The test indenter is a sphere, and the expression of the skin elastic modulus E is: Among them, F n represents the normal force, v is the Poisson's ratio of the skin, δ represents the normal penetration depth of the skin, and R represents the radius of the test indenter; The expression of the two-term friction model is: B＝α In the formula, F total represents the total friction force, F is the elastic modulus of the skin, τ0 is the inherent interface shear strength, α is the pressure coefficient, β is the skin viscosity coefficient, R is the radius of the test indenter, and W is the constant force load; Wherein, the load loading interval P = {W1, W2, ..., W m }, m is the total number of loading times; Based on the numerical iteration method, multiple powers are combined to solve the parameters k and n in the simplified two-term friction model, and the loading interval P={W1,W2,…,W m K = {k1, k2, …, k} m } and N={n1,n2,…,n m }, get the average value The method of establishing a friction force response model based on skin characteristics according to the continuous image deformation field, skin force data and two friction models includes: Combining the skin stretch value-time curve △XT and force data F x -T, F z -T performs simultaneous domain analysis, fuses the skin characteristic index and the two friction models, and establishes a friction force response model based on skin characteristics kW n ∝△X.

2. The interactive method for measuring skin friction performance according to claim 1, characterized in that: The speckle mark is a disordered speckle mark with black dots as elements. The control test indenter rubs against the skin surface to collect an image of the skin surface, including: Controlling the test indenter to rub against the skin surface, so that the dot speckle is displaced as the skin deforms; Skin images with circular speckles are continuously acquired, and the brightness and contrast of the continuously acquired images are adjusted, and filtering is performed to obtain speckle images.

3. The interactive method for measuring skin friction performance according to claim 2, characterized in that: The step of acquiring a continuous image deformation field according to the collected image comprises: Performing stereo matching processing on the continuous speckle images to obtain a continuous deformation field of the speckle that changes with time; A skin stretch value-time curve ΔXT is obtained according to the speckle continuous deformation field.

4. The interactive method for measuring skin friction performance according to claim 1, characterized in that: The step of obtaining the skin force data during the friction between the test indenter and the skin comprises: During the movement of the test head, the force data in the three directions of X, Y and Z are obtained by the six-dimensional force sensor; wherein the force data includes the tangential force-time curve F in the same direction as the movement direction. x -T, and the normal force-time curve F in the same direction as the loading z -T.

5. An interactive system for measuring skin friction performance, applied to the interactive method for measuring skin friction performance according to any one of claims 1 to 4, characterized in that: include: Robotic arm; A test pressure head, fixed at the end of the mechanical arm, for contacting with the skin; An industrial camera assembly, used to collect images of the skin when it is in contact with the test indenter; wherein a speckle mark is provided on the surface of the skin; A six-dimensional force sensor, disposed at the end of the mechanical arm, for obtaining the friction force generated when the test pressure head contacts the skin; The control host side is used to control the moving trajectory of the robotic arm, receive the image information collected by the industrial camera component and the friction information collected by the six-dimensional force sensor, and build a friction response model based on skin characteristics according to the received information.

6. The interactive system for measuring skin friction properties according to claim 5, characterized in that: The industrial camera assembly includes two CMOS industrial cameras, the two CMOS industrial cameras are arranged at the same level, and the intersection of the sight lines of the two CMOS industrial cameras falls on the target skin area; the target skin area is an area with a speckle mark; and / or, The test pressure head is in the shape of a sphere, a hemisphere or a cube.

Images