Method, device and medium for adjusting posture of end of flexible object working robot

Abstract

The present invention discloses a posture adjustment method, device and medium for the end of a flexible object operation robot, wherein the method comprises: conducting experiments on the flexible object to obtain mechanical performance parameters; constructing a coordinate system, and establishing a relationship model between the surface normal vector and six-dimensional force data and mechanical performance parameters based on the constructed coordinate system; collecting six-dimensional force data in real time during the flexible object operation process, and obtaining the surface normal vector based on the collected six-dimensional force data and the relationship model; obtaining the end posture of the robot in real time, calculating the rotation vector of the robot's sixth axis vector and the surface normal vector, and calculating the expected posture of the next control cycle based on the rotation vector. The posture adjustment method proposed in the present invention can be used to adjust the end posture of the robot to the expected normal direction of the contact area with the flexible object in real time during a given trajectory motion, and can provide good working results in combination with the expected planned trajectory. The present invention can be widely used in the technical field of flexible object contact friction equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible object contact friction equipment, and in particular to a posture adjustment method, device and medium for a terminal end of a flexible object working robot. Background Art

[0002] In application scenarios such as medical rehabilitation, health massage, and beauty care, human-machine contact operations often require maintaining the correct posture and achieving contact operations along a pre-planned path under the action of normal force.

[0003] Existing literature typically uses depth cameras to reconstruct surfaces. Hand-eye calibration is used to obtain the rotation matrix between the robot and the camera. The surface normal is then calculated and the trajectory is planned along the waypoints to adjust the robot's posture. However, depth cameras often have large depth-direction errors, resulting in inaccurate surface normal information, which can lead to errors in the posture and pathpoints during the operation.

[0004] For robotic arm posture adjustment, existing research uses six-dimensional force sensors to construct a relationship model between unknown surface normals and six-dimensional forces, which is widely used in machining scenarios such as grinding and polishing. However, these applications propose relationship models based on rigid bodies, such as the model proposed by Jiang in "Active Tracking Unknown Surface Based on Force Control for Robot." This model assumes point contact between the robotic arm and the rigid object. However, a corresponding relationship model has not yet been established for flexible objects such as human skin. Summary of the Invention

[0005] 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 a posture adjustment method, device and medium for the end of a flexible object working robot.

[0006] The first technical solution adopted by the present invention is:

[0007] A method for adjusting the posture of a flexible object working robot end, wherein the robot end is provided with an end effector, the contact portion between the end effector and the flexible object is a spherical surface, and a six-dimensional force sensor is provided between the robot end and the end effector, the six-dimensional force sensor being used to collect six-dimensional force data of the end effector;

[0008] The posture adjustment method comprises the following steps:

[0009] Conduct experiments on flexible objects (such as human skin) to obtain mechanical performance parameters;

[0010] Construct a coordinate system, and establish a relationship model between the surface normal vector and six-dimensional force data and mechanical performance parameters based on the constructed coordinate system;

[0011] During the operation of flexible objects, six-dimensional force data is collected in real time, and the representation parameters of the surface normal vector are obtained based on the collected six-dimensional force data and the relationship model;

[0012] The robot's end posture is acquired in real time, the rotation vector of the robot's sixth axis vector and the surface normal vector is calculated, the expected posture of the next control cycle is calculated based on the rotation vector, and a command is input to the robot to realize posture adjustment.

[0013] Furthermore, the experiment on the flexible object to obtain mechanical performance parameters includes:

[0014] Perform an indentation test on a flexible object to measure the equivalent Young's modulus E of the flexible object * :

[0015]

[0016] Among them, k z is the initial contact stiffness, which is obtained from the slope of the initial unloading curve of the indentation. A is the contact area, which can be obtained from the Hertz theory:

[0017]

[0018] Use the adhesion friction data of a flexible object to fit the parameters in the Wolfram adhesion friction formula:

[0019]

[0020] Where τ0 is the initial interface shear strength, γ is the pressure coefficient, R is the radius of the end effector sphere, W is the positive normal pressure, and F adh is the adhesive friction force, and the fitted parameters are τ0 and γ.

[0021] Furthermore, the constructing of the coordinate system includes:

[0022] Construct the robot base coordinate system O b , sensor coordinate system O s , moving coordinate system O m , equivalent point coordinate system O e And calculate the coordinate system O m' .

[0023] Furthermore, the sensor coordinate system is the six-dimensional force sensor's own coordinate system. The unit vector of the end rotation vector read by the robot is The magnitude of the rotation vector is θ, and the rotation matrix It can be obtained from the Rodrigues formula:

[0024]

[0025] in, O b to O s The rotation matrix, I is the identity matrix, K is the rotation vector The matrix obtained by constructing the skew-symmetric matrix is:

[0026]

[0027] Among them, v x 、v y With v z for In the base coordinate system O b Components of each axis.

[0028] Usually, the movement of the robot arm is divided into two directions, one is along the sixth axis of the robot arm, called the axial direction, and the other is perpendicular to the sixth axis of the end, called the feed direction. m Given the feed direction The established coordinate system is b x m for The unit vector of b x m O m The x-axis unit vector in the base coordinate system O b The following expression, In the base coordinate system O b The z-axis of the mobile coordinate system and the sensor coordinate system O s The z-axis is in the same direction, assuming b z s O s The z-axis unit vector of the coordinate system is in the robot base coordinate system O b The following expression, b z m O m The z-axis unit vector in the base coordinate system O b The following expressions are:

[0029]

[0030] set up b y m O m The y-axis unit vector of the coordinate system is in the robot base coordinate system O b The following expression, b y m From the other two axes we get:

[0031]

[0032] O mThe unit vectors of the three axes in the coordinate system are expressed in the base coordinate system as follows: b x m , b y m and b z m , there is O b to O m The rotation matrix for:

[0033]

[0034] Equivalent point coordinate system O e Established in the contact area center, O e The z-axis is simultaneously aligned with the surface normal vector Same direction, In O m The following expression, where α and β are geometric parameters and R is the radius of the end sphere, is:

[0035]

[0036] set up m z e O e The z-axis unit vector of the coordinate system is at O m The following expressions are:

[0037]

[0038] set up m x e O e The x-axis unit vector of the coordinate system is at O m The following representation is parallel to x m o m z m flat, m y m O m The y-axis unit vector is represented as:

[0039] m x e = m y m × m z e

[0040] m y e pass m x e and m z e It turns out that:

[0041] m ye = m z e × m x e

[0042] Then there is O m to O e The rotation matrix for:

[0043]

[0044] Calculation coordinate system O m' The purpose of establishing the model is to facilitate the establishment of m' With O m The rotation matrix is ​​the identity matrix, O m' The origin of the equivalent coordinate system is the same as that of the equivalent coordinate system, and there is a transformation matrix

[0045]

[0046] Where l is the moving coordinate system O m The distance from the origin to the center of the sphere.

[0047] Furthermore, the relationship model between the surface normal vector and the six-dimensional force data and mechanical performance parameters is established based on the constructed coordinate system, including:

[0048] Furthermore, the relationship model between the surface normal vector and the six-dimensional force data and mechanical performance parameters is established based on the constructed coordinate system, including:

[0049] For the force analysis of the contact area, the contact positive pressure distribution in the contact area is:

[0050]

[0051] Where p0 is a constant representing the maximum pressure at the origin, a and b are the major and minor axes of the elliptical contact area; x e 、y e It is the coordinate representation of a point in the elliptical area;

[0052] Based on the binomial friction theory, the interfacial shear resistance is mainly caused by the transient interaction of the van der Waals force in the contact area. It is assumed that the van der Waals force is the same at each position on the contact surface, and the interfacial shear strength τ is used to characterize the distribution of the van der Waals force.

[0053] From the symmetry, we can see that the force condition is equivalent to O e At the origin, the force is:

[0054]

[0055] Where, O e The x-axis and y-axis forces in the coordinate system, O e The y-axis moment in the coordinate system;

[0056] The torque generated by the positive pressure on the y-axis of the equivalent point coordinate system is 0, and the torque generated by the van der Waals force on the equivalent point is By integrating over the contact area:

[0057]

[0058] Where a H is the contact radius, and according to Hertz contact theory:

[0059]

[0060] Where, E * is the equivalent Young's modulus, W is the positive normal pressure, that is, Through the rotation matrix With O m Coordinate system six-dimensional force F m Relationships are sought;

[0061] The interfacial shear strength τ is obtained by the following formula:

[0062]

[0063] Where τ0 is the initial interface shear strength, W is the positive normal pressure, and γ is the pressure coefficient;

[0064] Calculation coordinate system O m' The forces on are:

[0065]

[0066] Where, Respectively represent O m The six-dimensional force in the coordinate system, Respectively represent O m' The six-dimensional forces in the coordinate system;

[0067] By moving the coordinate system O m Modeling relationships:

[0068]

[0069] Where α and β are geometric parameters, l is O m The distance to the center of the spherical end;

[0070] Calculation coordinate system O m' Lower three-dimensional moment nm′ Expressed as:

[0071]

[0072] Where n e is the three-dimensional moment in the equivalent point coordinate system.

[0073] Furthermore, the obtaining of the surface normal vector according to the collected six-dimensional force data and the relationship model includes:

[0074] A nonlinear equation group is obtained based on the six-dimensional force data and the relational model. The particle swarm algorithm is used to solve the nonlinear equation group, and the result of the solution is the surface normal vector.

[0075] Furthermore, the particle swarm algorithm is used to solve the nonlinear equations, and the result of the solution is a surface normal vector, including:

[0076] The particle swarm algorithm is used to solve the nonlinear equations. Each particle has two dimensions, α and β. Let the position X of the i-th particle be i for:

[0077] X i =(α i ,β i )

[0078] The velocity of the i-th particle is V i :

[0079] V i =(v i1 ,v i2 )

[0080] Let the optimal position searched by the i-th particle be P i,pbest , the optimal position searched by the group is P gbest , the speed update formula of the particle swarm algorithm is:

[0081]

[0082] Where ω is the inertia weight, c1 and c2 are acceleration coefficients, and r1 and r2 are random numbers in the interval [0,1]. represents the historical optimal position of particle i in the kth iteration, represents the historical optimal position of the group in the kth iteration.

[0083] Furthermore, the real-time acquisition of the robot's end posture, calculation of the rotation vector between the robot's sixth axis vector and the surface normal vector, and calculation of the expected posture of the next control cycle according to the rotation vector include:

[0084] According to the surface normal vector, the corresponding rotation vector unit vector is The magnitude of the rotation vector is θ1, and then the rotation matrix is ​​obtained by the Rodrigues formula

[0085]

[0086] Where, is the rotation vector The matrix obtained by constructing the skew-symmetric matrix is:

[0087]

[0088] Where, v 1x 、v 1y With v 1z for In the moving coordinate system O m Components of each axis;

[0089] Since the robot position control needs to obtain the six-dimensional position {x, y, z, r x ,r y ,r z}, the robot uses the rotation vector method, that is, r x ,r y ,r z It is represented by a rotation vector, so it is necessary to obtain the rotation matrix R from the base coordinate system to the target pose tar ,have:

[0090]

[0091] According to the Rodrigues formula, the rotation vector corresponding to the target posture is obtained Let its unit vector be Its size is θ tar ,have:

[0092]

[0093] at last That is That is, the corresponding posture r x ,r y ,r z ,{x,y,z,r x ,r y ,r z}The movement command is input to the robot to achieve the target posture and complete the adjustment.

[0094] The second technical solution adopted by the present invention is:

[0095] A posture adjustment device for a terminal end of a flexible object working robot, comprising:

[0096] A robot, wherein an end effector is provided at the end of the robot, and the contact point between the end effector and the flexible object is a spherical surface;

[0097] A six-dimensional force sensor is provided between the end of the robot and the end effector to collect six-dimensional force data;

[0098] The control module is used to construct a coordinate system and establish a relationship model between the surface normal vector and six-dimensional force data and mechanical performance parameters based on the constructed coordinate system; during the operation of the flexible object, the six-dimensional force data is collected in real time, and the surface normal vector is obtained based on the collected six-dimensional force data and the relationship model; the end posture of the robot is obtained in real time, and the rotation vector of the robot's sixth axis vector and the surface normal vector is calculated, and the expected posture of the next control cycle is calculated based on the rotation vector; wherein the mechanical performance parameters are obtained through preliminary experimental tests.

[0099] The third technical solution adopted by the present invention is:

[0100] A posture adjustment device for a terminal end of a flexible object working robot, comprising:

[0101] at least one processor;

[0102] at least one memory for storing at least one program;

[0103] When the at least one program is executed by the at least one processor, the at least one processor implements the above method.

[0104] The fourth technical solution adopted by the present invention is:

[0105] A computer-readable storage medium stores a program executable by a processor, wherein the program executable by the processor is used to perform the method described above when executed by the processor.

[0106] The beneficial effect of the present invention is that the real-time posture adjustment method proposed in the present invention can be used to adjust the end posture of the robot (i.e., the robotic arm) to the desired normal direction of the contact area with the flexible object in real time during a given trajectory movement, and can provide good working effects in combination with the desired planned trajectory. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following introduction is made to the drawings of the embodiments of the present invention or the related technical solutions in the prior art. 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 any creative work.

[0108] Figure 1 This is an overall flow chart of a method for adjusting the terminal posture of a flexible object working robot based on a six-dimensional force sensor in an embodiment of the present invention.

[0109] Figure 2 Schematic diagram of sensor coordinates in a method for adjusting the terminal posture of a flexible object working robot based on a six-dimensional force sensor in an embodiment of the present invention.

[0110] Figure 3 Schematic diagram of the working method of the terminal posture adjustment method of the flexible object working robot based on the six-dimensional force sensor in an embodiment of the present invention.

[0111] Figure 4 This is a simplified diagram of a flexible object operation method of a flexible object operation robot based on a six-dimensional force sensor in an embodiment of the present invention.

[0112] Figure 5 This is a relationship diagram between the moving coordinate system and the equivalent point coordinate system of the terminal posture adjustment method of the flexible object working robot based on the six-dimensional force sensor in an embodiment of the present invention.

[0113] Figure 6 This is a diagram showing the relationship between the moving coordinate system and the calculation coordinate system of the terminal posture adjustment method of the flexible object working robot based on the six-dimensional force sensor in an embodiment of the present invention.

[0114] Figure 7 This is a microscopic force approximation diagram of the terminal posture adjustment method of the flexible object working robot based on the six-dimensional force sensor in an embodiment of the present invention. DETAILED DESCRIPTION

[0115] The embodiments of the present invention are described in detail below, examples of which 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 limiting the present invention. The step numbers in the following embodiments are provided for ease of explanation only and do not limit the order of the steps. The order of execution of the steps in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0116] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They 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. Therefore, they cannot be understood as limitations on the present invention.

[0117] In the description of the present invention, the meaning of "several" is one or more, the meaning of "many" is two or more, and "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of the first and the second, it is only 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. In addition, "and / or" describes the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship.

[0118] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting 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.

[0119] In response to the existing technical problems, the present invention proposes a posture adjustment method for the end of a flexible object working robot based on a six-dimensional force sensor, which obtains six-dimensional force sensor data in real time, substitutes the relational model under a predetermined path and calculates the current surface normal vector, providing precise posture control for the actual working process.

[0120] This invention was funded by the Guangdong Basic and Applied Basic Research Fund, which is funded by the Guangdong Basic and Applied Basic Research Fund Committee with project number 2023A1515010682. The researchers received support from this fund project.

[0121] Please check Figure 1 The present invention provides a method for adjusting the posture of a flexible object handling robot end based on a six-dimensional force sensor, comprising the following steps:

[0122] Step S1: Measure mechanical properties such as equivalent Young's modulus and pressure coefficient through indentation and tensile tests:

[0123] In some embodiments, step S1 specifically includes the following steps:

[0124] S11. Perform an indentation test on the workpiece to measure the equivalent Young's modulus E of the flexible object. * :

[0125] where k z is the initial contact stiffness, which is obtained from the slope of the initial unloading curve of the indentation. A is the contact area, which can be obtained from the Hertz theory:

[0126]

[0127] S12. Use the flexible object adhesion friction data to fit the parameters of the Wolfram adhesion friction formula: initial interface shear strength τ0 and pressure coefficient γ:

[0128]

[0129] Where τ0 is the initial interface shear strength, γ is the pressure coefficient, R is the radius of the end effector sphere, W is the normal force, and the fitted parameters are τ0 and γ.

[0130] Step S2: Establish the following five coordinate systems: robot base coordinate system O b , sensor coordinate system O s , moving coordinate system O m , equivalent point coordinate system O e And calculate the coordinate system O m' .

[0131] 1) See Figure 2 , sensor coordinate system O s The sensor hardware has its own coordinate system, which can be used to read the six-dimensional force in the sensor coordinate system directly through instructions. The robot arm can read the sixth axis posture {x, y, z, r x ,r y ,r z}, r x ,r y ,r z It is expressed by a rotation vector, and the terminal rotation vector unit vector is The magnitude of the rotation vector is θ, and the rotation matrix It can be obtained from the Rodrigues formula:

[0132]

[0133]

[0134] where v x 、v y With v z for In the base coordinate system O b Components of each axis.

[0135] 2) See Figure 3 , robot base coordinate system O b With the moving coordinate system O m like Figure 3 As shown, to establish the mobile coordinate system O m It is necessary to obtain the rotation matrix from the base coordinate system to the mobile coordinate system It is known that there is O m Given the feed direction The established coordinate system is b x m for The unit vector of Figure 3 , assuming that dir is the end moving direction, let dir=(1,0,0), and set it to be calculated:

[0136]

[0137]

[0138]

[0139] That is to find out

[0140] 3) See Figure 4 The spherical indenter moves along the surface of the flexible object, and the indenter and the flexible object form a contact area. The contact area is approximately elliptical. A straight line NN' is formed through the center O of the spherical indenter and the center of the ellipse. NN' is the surface normal vector based on which the posture is adjusted in this paper. NN' intersects the bottom of the indenter at point P, and the model is equivalent to Figure 5 , there is a moving coordinate system O m To the equivalent point coordinate system O e The rotation matrix Let R be the radius of the end sphere, and we can get:

[0141]

[0142]

[0143] m x e = m y m × m z e

[0144] m y e = m z e × m x e

[0145] 4) See Figure 6 Calculation coordinate system O m' , which has only a translation relationship with the moving coordinate system, then

[0146]

[0147] Step S3: Establish a relationship model between the surface normal vector and the six-dimensional force data and the mechanical performance parameters measured in step S1 based on the coordinate system established in step S2, and substitute the data into:

[0148] See also Figure 7 Based on the binomial friction theory, the approximate force situation of the contact area is analyzed, where A is the contact area, τ is the interface shear strength, and the torque generated by the positive pressure p on the y-axis of the equivalent point coordinate system is 0. From the symmetry, it can be seen that The moment M generated by the van der Waals force on the equivalent point ye It can be obtained by integrating the contact area:

[0149]

[0150]

[0151]

[0152] Among them, τ0 and γ are obtained in step S1, and W is the positive normal pressure, that is, Calculated by the following formula:

[0153]

[0154] in, O e to O m The rotation matrix, F m is the six-dimensional force in the moving coordinate system, and similarly we have

[0155] 2) See Figure 6 , the calculation coordinate system force is as follows:

[0156]

[0157] Model relationships by moving coordinate systems:

[0158]

[0159] The calculation coordinate system O m' Lower three-dimensional moment n m′ Expressed as:

[0160]

[0161] n e O e The moment in the coordinate system.

[0162] Step S4: Particle swarm algorithm solves nonlinear equations in real time:

[0163] Each particle has two dimensions, namely α and β. Let the position X of the i-th particle be i for:

[0164] X i =(α i ,β i )

[0165] The velocity of the i-th particle is V i :

[0166] V i =(v i1 ,v i2 )

[0167] Let the optimal position searched by the i-th particle be P i,pbest , the optimal position searched by the group is P gbest , the speed update formula of the particle swarm algorithm is:

[0168]

[0169] Where ω is the inertia weight, usually 1.49445, c1 and c2 are acceleration coefficients, c1 is 1.6, and c2 is 1.8.

[0170] The object to be solved is a nonlinear system of equations, the optimization goal is to minimize the difference between the two sides of the equation, and the fitness function is f(α,β):

[0171]

[0172]

[0173]

[0174] Real-time calculation iteration process Figure 1 shown.

[0175] Step S5: Obtain the end-of-arm posture in real time, calculate the rotation vector between the sixth-axis vector of the manipulator and the surface normal vector, and calculate the desired posture of the next control cycle based on the rotation vector. Input the command to the robot to achieve posture adjustment:

[0176] 1) Normal vector obtained from S4 With z m Find the corresponding rotation vector unit vector is The magnitude of the rotation vector is θ1, and then the rotation matrix is ​​obtained by the Rodrigues formula

[0177]

[0178]

[0179] where v 1x 、v 1y With v 1z for In the moving coordinate system O m Components of each axis.

[0180] 2) Get the rotation matrix R from the base coordinate system to the target pose tar :

[0181]

[0182] According to the Rodrigues formula, the rotation vector corresponding to the target posture is obtained Let its unit vector be Its size is θ tar ,have:

[0183]

[0184] at last That is That is, the corresponding target posture r x ,r y ,r z ,{x,y,z,r x ,r y ,r z}The movement command is input to the robot to achieve the target posture and complete the adjustment.

[0185] This embodiment further provides a posture adjustment device for a terminal end of a flexible object working robot, comprising:

[0186] A robot, wherein an end effector is provided at the end of the robot, and the contact point between the end effector and the flexible object is a spherical surface;

[0187] A six-dimensional force sensor is provided between the end of the robot and the end effector to collect six-dimensional force data;

[0188] The control module is used to construct a coordinate system and establish a relationship model between the surface normal vector and six-dimensional force data and mechanical performance parameters based on the constructed coordinate system; during the operation of the flexible object, the six-dimensional force data is collected in real time, and the surface normal vector is obtained based on the collected six-dimensional force data and the relationship model; the end posture of the robot is obtained in real time, and the rotation vector of the robot's sixth axis vector and the surface normal vector is calculated, and the expected posture of the next control cycle is calculated based on the rotation vector; wherein the mechanical performance parameters are obtained through preliminary experimental tests.

[0189] A posture adjustment device for the end of a flexible object working robot in this embodiment can execute a posture adjustment method for the end of a flexible object working robot provided by an embodiment of the method of the present invention, can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.

[0190] This embodiment further provides a posture adjustment device for a terminal end of a flexible object working robot, comprising:

[0191] at least one processor;

[0192] at least one memory for storing at least one program;

[0193] When the at least one program is executed by the at least one processor, the at least one processor implements Figure 1 The method shown.

[0194] A posture adjustment device for the end of a flexible object working robot in this embodiment can execute a posture adjustment method for the end of a flexible object working robot provided by an embodiment of the method of the present invention, can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.

[0195] The present application also discloses a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs Figure 1 The method shown.

[0196] This embodiment also provides a storage medium storing instructions or programs that can execute a posture adjustment method for the end of a flexible object working robot provided by an embodiment of the method of the present invention. When the instructions or program are run, any combination of implementation steps of the method embodiment can be executed, and the corresponding functions and beneficial effects of the method can be obtained.

[0197] In some optional 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 in an exemplary manner for the purpose of providing a more comprehensive understanding of the technology. The disclosed method is not limited to the operation and logic flow presented herein. Optional embodiments are contemplated in which the order of the various operations is changed and the sub-operations described as a part of a larger operation are performed independently.

[0198] Furthermore, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise indicated, 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 will also be understood that a detailed discussion of the actual implementation of each module is not necessary for understanding the present invention. More specifically, given the properties, functions, and internal relationships of the various functional modules in the devices disclosed herein, the actual implementation of the module will be understood within the ordinary skill of an engineer. Therefore, a person skilled in the art using ordinary skill will be able to implement the present invention set forth in the claims without undue experimentation. It will also be 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.

[0199] 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 and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0200] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0201] More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk cartridge (magnetic devices), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable medium may even be 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 processing in another suitable manner as necessary, and then stored in a computer memory.

[0202] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0203] In the above description of this specification, reference to the terms "one embodiment / example," "another embodiment / example," or "certain embodiments / examples" 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 suitable manner in any one or more embodiments or examples.

[0204] While 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 invention, and that the scope of the invention is defined by the claims and their equivalents.

[0205] 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 can 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.

Claims

1. A method for adjusting the posture of a flexible object working robot end, characterized in that: An end effector is provided at the end of the robot, the contact point between the end effector and the flexible object is a spherical surface, and a six-dimensional force sensor is provided between the end of the robot and the end effector, and the six-dimensional force sensor is used to collect six-dimensional force data; The posture adjustment method comprises the following steps: Conduct experiments on flexible objects to obtain mechanical performance parameters; Construct a coordinate system, and establish a relationship model between the surface normal vector and six-dimensional force data and mechanical performance parameters based on the constructed coordinate system; During the operation of flexible objects, six-dimensional force data is collected in real time, and the surface normal vector is obtained based on the collected six-dimensional force data and the relationship model; Acquire the robot's end-point posture in real time, calculate the rotation vector between the robot's sixth axis vector and the surface normal vector, and calculate the expected posture of the next control cycle based on the rotation vector; The experiment on the flexible object to obtain mechanical performance parameters includes: Perform an indentation test on a flexible object to measure the equivalent Young's modulus E of the flexible object * : Where k z is the initial contact stiffness, A is the contact area; Use the adhesion friction data of a flexible object to fit the parameters in the Wolfram adhesion friction formula: Where τ0 is the initial interface shear strength, γ is the pressure coefficient, R is the radius of the end effector sphere, W is the positive normal pressure, and F adh is the adhesive friction.

2. The method for adjusting the posture of a flexible object handling robot end according to claim 1, characterized in that: The constructing of the coordinate system includes: Construct the robot base coordinate system O b , sensor coordinate system O s , moving coordinate system O m , equivalent point coordinate system O e And calculate the coordinate system O m' .

3. The method for adjusting the posture of a flexible object handling robot end according to claim 2, characterized in that: The relationship model between the surface normal vector, six-dimensional force data, and mechanical performance parameters is established based on the constructed coordinate system, including: For the force analysis of the contact area, the contact positive pressure distribution in the contact area is: Where p0 is a constant representing the maximum pressure at the origin, a and b are the major and minor axes of the elliptical contact area; x e 、y e is the coordinate of a point in the elliptical area; Based on the binomial friction theory, the interfacial shear resistance is mainly caused by the transient interaction of the van der Waals force in the contact area. It is assumed that the van der Waals force is the same at each position on the contact surface, and the interfacial shear strength τ is used to characterize the distribution of the van der Waals force. From the symmetry, we can see that the force condition is equivalent to O e At the origin, the force is: Where, O e The x-axis and y-axis forces in the coordinate system, O e The y-axis moment in the coordinate system; The torque generated by the positive pressure on the y-axis of the equivalent point coordinate system is 0, and the torque generated by the van der Waals force on the equivalent point is By integrating over the contact area: Where a H is the contact radius; R is the radius of the end effector sphere; The interfacial shear strength τ is obtained by the following formula: Where τ0 is the initial interface shear strength, W is the positive normal pressure, and γ is the pressure coefficient; Calculation coordinate system O m' The forces acting on are: Where, Respectively represent O m The six-dimensional force in the coordinate system, Respectively represent O m' The six-dimensional forces in the coordinate system; By moving the coordinate system O m Modeling relationships: Where α and β are geometric parameters, l is O m The distance to the center of the spherical end; Calculation coordinate system O m' Lower three-dimensional moment n m′ Expressed as: Where n e is the three-dimensional moment in the equivalent point coordinate system.

4. The method for adjusting the posture of a flexible object handling robot end according to claim 1, characterized in that: The obtaining of the surface normal vector according to the collected six-dimensional force data and the relationship model includes: A nonlinear equation group is obtained based on the six-dimensional force data and the relational model. The particle swarm algorithm is used to solve the nonlinear equation group, and the result of the solution is the surface normal vector.

5. The method for adjusting the posture of a flexible object handling robot end according to claim 4, characterized in that: The particle swarm algorithm is used to solve the nonlinear equations, and the result of the solution is the surface normal vector, including: The particle swarm algorithm is used to solve the nonlinear equations. Each particle has two dimensions, α and β. Let the position X of the i-th particle be i for: X i ＝(α i ,β i ) The velocity of the i-th particle is V i : V i =(v i1 ,v i2 ) Let the optimal position searched by the i-th particle be P i,pbest , the optimal position searched by the group is P gbest , the speed update formula of the particle swarm algorithm is: Where ω is the inertia weight, c1 and c2 are acceleration coefficients, and r1 and r2 are random numbers in the interval [0,1]. represents the historical optimal position of particle i in the kth iteration, represents the historical optimal position of the group in the kth iteration.

6. The method for adjusting the posture of a flexible object handling robot end according to claim 1, characterized in that: The real-time acquisition of the end posture of the robot, calculation of the rotation vector of the sixth axis vector of the robot and the surface normal vector, and calculation of the expected posture of the next control cycle according to the rotation vector include: According to the surface normal vector, the corresponding rotation vector unit vector is The magnitude of the rotation vector is θ1, and then the rotation matrix is ​​obtained by the Rodrigues formula Where, is the rotation vector The matrix obtained by constructing the skew-symmetric matrix; Since the robot position control needs to obtain the six-dimensional position {x, y, z, r x ,r y ,r z }, the robot uses the rotation vector method, that is, r x ,r y ,r z It is represented by a rotation vector, so it is necessary to obtain the rotation matrix R from the base coordinate system to the target pose tar ,have: According to the Rodrigues formula, the rotation vector corresponding to the target posture is obtained Let its unit vector be Its size is θ tar ,have: at last That is That is, the corresponding posture r x ,r y ,r z ,{x,y,z,r x ,r y ,r z }The movement command is input to the robot to achieve the target posture and complete the adjustment.

7. A posture adjustment device for the end of a flexible object working robot, characterized in that: include: A robot, wherein an end effector is provided at the end of the robot, and the contact point between the end effector and the flexible object is a spherical surface; A six-dimensional force sensor is provided between the end of the robot and the end effector to collect six-dimensional force data; A control module is used to construct a coordinate system and establish a relationship model between the surface normal vector and six-dimensional force data and mechanical performance parameters based on the constructed coordinate system; During the flexible object operation process, six-dimensional force data is collected in real time, and the surface normal vector is obtained based on the collected six-dimensional force data and the relationship model; the end posture of the robot is obtained in real time, the rotation vector of the robot's sixth axis vector and the surface normal vector is calculated, and the expected posture of the next control cycle is calculated based on the rotation vector; Among them, the mechanical properties parameters are obtained by the following methods; Perform an indentation test on a flexible object to measure the equivalent Young's modulus E of the flexible object * : Where k z is the initial contact stiffness, A is the contact area; Use the adhesion friction data of a flexible object to fit the parameters in the Wolfram adhesion friction formula: Where τ0 is the initial interface shear strength, γ is the pressure coefficient, R is the radius of the end effector sphere, W is the positive normal pressure, and F adh is the adhesive friction.

8. A posture adjustment device for the end of a flexible object working robot, characterized in that: include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the method according to any one of claims 1 to 6.

9. A computer-readable storage medium storing a program executable by a processor, characterized in that: The processor-executable program is used to perform the method according to any one of claims 1 to 6 when executed by the processor.

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