Contact analysis method and device for mechanical arm to grab non-fixed posture object and medium

Abstract

The invention discloses a contact analysis method and device for a mechanical arm to grab a non-fixed posture object and a medium. Relates to the technical field of mechanical arm grabbing, and solves the problem of low precision of a contact response result caused by simplification of a to-be-grabbed object. The tail end of the mechanical arm and the non-fixed posture object are respectively formed by combining a plurality of polyhedrons, so that the precision of geometric expression is improved, and a more accurate basis is provided for subsequent contact detection. And a nonlinear damping model is introduced, so that energy loss and mechanical properties in the contact process are simulated more truly, and the accuracy of contact force calculation is improved. And by analyzing the contact state response, the grabbing stability and safety of the mechanical arm can be evaluated, and a reliable basis is provided for subsequent grabbing control.

Description

Technical Field

[0001] The present application relates to the field of robotic arm grasping technology, and in particular to a contact analysis method, device and medium for a robotic arm to grasp an object in a non-fixed posture. Background Art

[0002] With the rapid development of industrial robot technology, robotic arms play an increasingly important role in industrial production, especially in the process of standardized production. However, in certain specific scenarios, robotic arms often need to grasp some non-fixed posture objects, such as scattered random incoming materials, mineral processing, etc. These targets are usually not standardized, and the size, position, shape, etc. of the incoming materials are relatively random, so they are called "non-fixed posture objects."

[0003] During the grasping process, it is inevitable that the robot arm will contact with the non-fixed posture object. Due to the non-specificity of the environment, this contact will cause complex dynamic responses. If not handled properly, it may lead to grasping failure at best, or damage the robot arm or cause more serious mechanical accidents at worst. Therefore, accurately analyzing the contact dynamic characteristics between the robot arm and the non-fixed posture object is crucial to the successful implementation of the grasping task.

[0004] The current contact dynamics analysis methods mainly include point model method, sphere model method and simplified polyhedron model method. The point model method simplifies the object into a mass point, which is simple to calculate but ignores the geometric shape and moment of inertia of the object, and has limited accuracy; the sphere model method simplifies the object into a sphere, and although it takes the volume of the object into account, its accuracy is still not ideal for the complex-shaped end of the robotic arm and non-fixed posture objects.

[0005] It can be seen that simplifying the object to be grasped leads to low accuracy of the contact response result, which is a technical problem that needs to be solved urgently by people in this field. Summary of the invention

[0006] The purpose of the present application is to provide a contact analysis method, device and medium for a robotic arm to grasp an object with a non-fixed posture, so as to solve the problem of low accuracy of contact response results caused by simplifying the object to be grasped.

[0007] In order to solve the above technical problems, the present application provides a contact analysis method for a robot arm grasping an object with a non-fixed posture, comprising:

[0008] Obtain the dynamic model of the robot arm based on the operating environment;

[0009] The end of the robot arm is represented as a combination of m polyhedrons, and the non-fixed posture object is represented as a combination of n polyhedrons, where m and n are positive integers greater than 1;

[0010] According to the real-time coordinates of the robotic arm and the non-fixed attitude object, it is sequentially determined whether any polyhedron corresponding to the robotic arm contacts any polyhedron corresponding to the non-fixed attitude object;

[0011] If there is contact, obtain the contact point where the two polyhedrons contact;

[0012] Obtain the contact force of the contact point according to the preset non-linear damping model;

[0013] Analyze the contact force according to the dynamic model to obtain the contact state response.

[0014] As an alternative solution, in the above contact analysis method for a robotic arm to grasp a non-fixed attitude object, the steps for establishing the dynamic model of the robotic arm are as follows:

[0015] Establish the generalized coordinates of the robotic arm with a 6-axis robotic arm , where q1 and q2 are the joint angles from the base coordinate system to the inter-arm rotation joint, q3 and q4 are the joint angles from the inter-arm rotation joint to the first arm end rotation joint, and q5 and q6 are the joint angles from the first arm end rotation joint to the end tool rotation joint;

[0016] Construct a dynamic model according to the dynamic equation;

[0017] The dynamic equation is: ;

[0018] In the formula, M is the mass matrix, C is the constraint matrix, G is the gravity matrix, T is the Coriolis matrix, is the linear damping matrix, , is the control input, is the acceleration vector, is the velocity vector;

[0019] Establish the moment of momentum from the center of mass of the robotic arm to the center of the end effector of the robotic arm;

[0020] The moment of momentum is expressed as: ;

[0021] In the formula, represents the moment of momentum, is the inertia tensor matrix of the inter-arm rotation joint, is the inertia tensor matrix of the first arm end rotation joint, is the inertia tensor moment of the end effector of the robotic arm, are the angular velocities of the corresponding components respectively;

[0022] Establish the inertia matrix of rotation from the end effector coordinate system of the robotic arm to the inter-arm rotation joint coordinate system.

[0023] As an alternative, in the above contact analysis method for a robotic arm to grasp an object with an unfixed posture, representing the end of the robotic arm as a combination of m polyhedrons and representing the object with an unfixed posture as a combination of n polyhedrons includes:

[0024] Representing the m polyhedrons divided by the actuator at the end of the robotic arm as a set V, , where represents the j-th polyhedron corresponding to the actuator at the end of the robotic arm, ;

[0025] Dividing the object with an unfixed posture into n polyhedrons, where n ≥ 2;

[0026] Representing the n polyhedrons obtained by dividing the object with an unfixed posture as a set , , where represents the i-th polyhedron corresponding to the object with an unfixed posture, .

[0027] As an alternative, in the above contact analysis method for a robotic arm to grasp an object with an unfixed posture, successively determining whether each polyhedron corresponding to the robotic arm contacts any one of the polyhedrons corresponding to the object with an unfixed posture according to the real-time coordinates of the robotic arm and the object with an unfixed posture includes:

[0028] Determining the edge feature vectors of each polyhedron corresponding to the robotic arm and each polyhedron corresponding to the object with an unfixed posture based on the real-time coordinates of the robotic arm and the object with an unfixed posture. Among them, for the polyhedron the vector corresponding to the -th edge is represented as the feature vector , then the set of feature vectors of all edges corresponding to the m polyhedrons divided by the actuator at the end of the robotic arm is , and for the polyhedron the vector corresponding to the l-th edge is represented as the feature vector , then the set of feature vectors of all edges corresponding to the n polyhedrons obtained by dividing the object with an unfixed posture is ;

[0029] Judging whether the number of intersection terms of is 0;

[0030] If not, determining that each polyhedron corresponding to the robotic arm contacts any one of the polyhedrons corresponding to the object with an unfixed posture;

[0031] If so, determining that each polyhedron corresponding to the robotic arm does not contact any one of the polyhedrons corresponding to the object with an unfixed posture.

[0032] As an alternative, in the above contact analysis method for a robotic arm to grasp an object with a non-fixed posture, obtaining the contact force at the contact point according to the preset non-linear damping model includes:

[0033] Defining two polyhedrons in contact through a non-linear damping model and the polyhedron , and obtaining the energy loss formula during the contact process of the two polyhedrons;

[0034] Taking the derivative of the energy loss formula to obtain the damping coefficient;

[0035] Obtaining the contact force according to the damping coefficient and the contact force calculation formula;

[0036] The contact force calculation formula is: ;

[0037] Wherein, represents the l-th edge of the i-th polyhedron corresponding to the object with a non-fixed posture, are respectively the normal vector, tangent vector and binormal vector corresponding to the edge , are respectively the corresponding damping coefficients, represents the contact collision force of the edge .

[0038] As an alternative, in the above contact analysis method for a robotic arm to grasp an object with a non-fixed posture, analyzing the contact force according to the dynamic model to obtain the contact state response includes:

[0039] Obtaining the first rotation equation of the end effector of the robotic arm through a preset angular momentum formula;

[0040] Obtaining the contact force between the end effector of the robotic arm and the edge of the object with a non-fixed posture according to the contact force, contact acceleration at the contact point and the first rotation equation;

[0041] Establishing a second rotation equation representing the object with a non-fixed posture;

[0042] Obtaining the contact constraint condition of the object with a non-fixed posture according to the contact force;

[0043] Solving the contact differential equation by the fourth-order Runge-Kutta method to obtain the contact response during the grasping process;

[0044] The contact differential equation is: ;

[0045] Wherein, h is the time step, are the coefficients of the Runge-Kutta method, representing the slopes at different times respectively. w represents the time step index, corresponding to the w-th step of the simulation, and y is the system state variable.

[0046] As an alternative, in the above contact analysis method for a robotic arm to grasp an object with a non-fixed posture, it further includes:

[0047] Select a corresponding preset elastic coefficient according to the robotic arm and the object with a non-fixed posture;

[0048] Determine the non-linear damping contact force according to the elastic coefficient.

[0049] To solve the above technical problems, the present application also provides a contact analysis device for a robotic arm to grasp an object with a non-fixed posture, including:

[0050] A preset module for obtaining the dynamic model of the robotic arm established based on the operating environment;

[0051] A simulation module for representing the end of the robotic arm as a combination of m polyhedrons and representing the object with a non-fixed posture as a combination of n polyhedrons, where m and n are positive integers greater than 1;

[0052] A judgment module for sequentially judging whether each polyhedron of the robotic arm contacts any one polyhedron of the object with a non-fixed posture according to the real-time coordinates of the robotic arm and the object with a non-fixed posture; if in contact, trigger the contact response module;

[0053] The contact response module for obtaining the contact point of the contact between the two polyhedrons;

[0054] A contact force calculation module for obtaining the contact force at the contact point according to a preset non-linear damping model;

[0055] An analysis module for analyzing the contact force according to the dynamic model to obtain a contact state response.

[0056] To solve the above technical problems, the present application also provides a contact analysis device for a robotic arm to grasp an object with a non-fixed posture, including:

[0057] A memory for storing a computer program;

[0058] A processor for implementing the steps of the above contact analysis method for a robotic arm to grasp an object with a non-fixed posture when executing the computer program.

[0059] To solve the above technical problems, the present application also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above contact analysis method for a robotic arm to grasp an object with a non-fixed posture are implemented.

[0060] The contact analysis method for a robotic arm to grasp an object with an un-fixed posture provided by this application. The end effector of the robotic arm and the object with an un-fixed posture are respectively composed of multiple polyhedrons, which improves the accuracy of geometric representation and provides a more accurate basis for subsequent contact detection. By introducing a non-linear damping model, the energy loss and mechanical properties during the contact process are more realistically simulated, and the accuracy of contact force calculation is improved. Through the analysis of the contact state response, the grasping stability and safety of the robotic arm can be evaluated, providing a reliable basis for subsequent grasping control.

[0061] In addition, this application also provides a device and a medium, corresponding to the above-mentioned contact analysis method for a robotic arm to grasp an object with an un-fixed posture, and the effects are the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] To more clearly illustrate the embodiments of this application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0063] Figure 1 It is a flowchart of a contact analysis method for a robotic arm to grasp an object with an un-fixed posture provided by an embodiment of this application;

[0064] Figure 2 It is a schematic diagram of a robotic arm dynamics model provided by an embodiment of this application;

[0065] Figure 3 It is a schematic diagram of the polyhedron representation of the end effector of a robotic arm provided by an embodiment of this application;

[0066] Figure 4 It is a schematic diagram of the polyhedron representation of an object with an un-fixed posture provided by an embodiment of this application;

[0067] Figure 5 It is a schematic diagram of polyhedron contact detection and intersection point determination provided by an embodiment of this application;

[0068] Figure 6 It is an energy loss curve diagram of a non-linear damping model provided by an embodiment of this application;

[0069] Figure 7 It is a flowchart of contact force calculation provided by an embodiment of this application;

[0070] Figure 8 It is a flowchart of contact response calculation provided by an embodiment of this application;

[0071] Figure 9It is a simulation result diagram of the contact force varying with time in the embodiment of the present invention;

[0072] Figure 10 It is a simulation result diagram of the position trajectory during the process of the robotic arm grasping an object with a non-fixed posture in the embodiment of the present invention;

[0073] Figure 11 It is a structural diagram of a contact analysis device for a robotic arm to grasp an object with a non-fixed posture provided in the embodiment of the present application;

[0074] Figure 12 It is a structural diagram of another contact analysis device for a robotic arm to grasp an object with a non-fixed posture provided in the embodiment of the present application. Detailed implementation manners

[0075] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present application.

[0076] The core of the present application is to provide a contact analysis method, device and medium for a robotic arm to grasp an object with a non-fixed posture.

[0077] In order to enable those skilled in the art to better understand the solution of the present application, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0078] To solve the above problems, the embodiment of the present application provides a contact analysis method for a robotic arm to grasp an object with a non-fixed posture, Figure 1 It is a flowchart of a contact analysis method for a robotic arm to grasp an object with a non-fixed posture provided in the embodiment of the present application. As Figure 1 shown, it includes:

[0079] S11: Obtain the dynamic model of the robotic arm established based on the operating environment;

[0080] S12: Represent the end of the robotic arm as a combination of m polyhedrons, and represent the object with a non-fixed posture as a combination of n polyhedrons, where m and n are positive integers greater than 1;

[0081] S13: Sequentially determine whether each polyhedron of the robotic arm contacts any one of the polyhedrons of the object with a non-fixed posture according to the real-time coordinates of the robotic arm and the object with a non-fixed posture;

[0082] S14: If there is contact, obtain the contact point where the two polyhedrons contact;

[0083] S15: Obtain the contact force at the contact point according to a preset non-linear damping model;

[0084] S16: Analyze the contact force according to the dynamics model to obtain the contact state response.

[0085] The embodiments of the present application are applicable to objects whose grasping positions and postures change in real time on a robotic arm (such as dynamic objects on a conveyor belt, free-falling objects, randomly placed parts, etc.). The shapes of the objects are irregular or the surfaces are complex (such as polyhedral industrial parts, flexible packages, stacked objects, etc.), and the postures of the objects are not pre-fixed.

[0086] Step S11 of obtaining the dynamics model of the robotic arm based on the operating environment refers to a mathematical model established based on the actual physical parameters of the robotic arm and the operating environment (such as gravity, friction, etc.), which is used to describe the motion law and dynamic characteristics of the robotic arm. It can be established by specific physical parameters (such as mass, inertia, joint angles, etc.) and the structural design of the robotic arm, combined with methods such as Newton-Euler equations or Lagrangian equations. In this step, through the establishment of the dynamics model, an accurate description of the motion state of the robotic arm is realized, providing a basis for subsequent contact analysis and control.

[0087] Step S12 of representing the end of the robotic arm and the non-fixed posture object as a polyhedron combination means decomposing the end of the robotic arm (such as a gripper) into multiple convex polyhedrons (such as cubes, prisms), and the non-fixed posture object is also decomposed into multiple non-polyhedrons to adapt to the irregular surface.

[0088] It can be segmented through a computer-aided design (CAD) model (such as decomposing the gripper into sub-structures such as fingertips and joints), and after exporting the STL file, it is converted into a polyhedron mesh. The non-fixed posture object can generate polyhedrons through three-dimensional point cloud segmentation. For example, the end of the robotic arm is decomposed into 5 polyhedrons (m = 5), and the object is decomposed into 10 polyhedrons (n = 10).

[0089] If the object deforms (such as a flexible package), the polyhedron combination needs to be updated in real time (through online point cloud registration). If the object is simple (such as a cube), it can be directly represented by a single polyhedron (n = 1).

[0090] Step S13 of real-time detecting polyhedron contact, the real-time coordinates refer to the fusion result of the robotic arm joint encoder data and the object pose sensor data, and the detection frequency can be set according to the industrial robot control cycle. The contact judgment is based on methods such as the edge feature vector and sign function of the polyhedron to improve the efficiency and accuracy.

[0091] Step S14 obtains the contact points and calculates the contact force. The contact points refer to the points where the polyhedron at the end of the robotic arm intersects or is tangent to the polyhedron of the non-fixed posture object during contact. They can be solved by methods of analytic geometry or numerical calculation. In this step, by determining the contact points, key information is provided for the subsequent calculation of the contact force.

[0092] Step S15 The non-linear damping model refers to a mechanical model that considers the energy loss during the contact process and is used to describe the relationship between the contact force, contact deformation, and contact velocity. The model parameters can be obtained by fitting experimental data or theoretical derivation. The calculation of the contact force is based on parameters such as the position, velocity, and material properties of the contact points and is carried out immediately after detecting the contact to ensure that the mechanical characteristics at the moment of contact can be accurately reflected.

[0093] Step S16 Analyze the contact force according to the dynamic model to obtain the contact state response, which includes the changes in the motion state of the robotic arm under the action of the contact force, such as position, velocity, and acceleration. It can be obtained by substituting the contact force into the dynamic equation for solution. In this step, by analyzing the contact state response, the grasping stability and safety of the robotic arm can be evaluated.

[0094] Through the contact analysis method for a robotic arm to grasp a non-fixed posture object provided by the embodiments of the present application, the end of the robotic arm and the non-fixed posture object are respectively composed of multiple polyhedrons, which improves the accuracy of geometric expression and provides a more accurate basis for subsequent contact detection. The introduction of the non-linear damping model more realistically simulates the energy loss and mechanical characteristics during the contact process and improves the accuracy of contact force calculation. By analyzing the contact state response, the grasping stability and safety of the robotic arm can be evaluated, providing a reliable basis for subsequent grasping control.

[0095] According to the above embodiments, in a specific implementation, for the contact analysis method of a robotic arm to grasp a non-fixed posture object, the steps for establishing the dynamic model of the robotic arm are as follows:

[0096] Establish the generalized coordinates of the robotic arm with a 6-axis robotic arm , where q1 and q2 are the joint angles from the base coordinate system to the inter-arm rotation joint, q3 and q4 are the joint angles from the inter-arm rotation joint to the first arm end rotation joint, and q5 and q6 are the joint angles from the first arm end rotation joint to the end tool rotation joint;

[0097] Construct the dynamic model according to the dynamic equation;

[0098] The dynamic equation is: ;

[0099] In the formula, M is the mass matrix, C is the constraint matrix, G is the gravity matrix, T is the Coriolis matrix, is the linear damping matrix, , is the control input, is the acceleration vector, is the velocity vector;

[0100] Establish the angular momentum from the center of mass of the robotic arm to the center of the end effector of the robotic arm;

[0101] The angular momentum is expressed as: ;

[0102] In the formula, represents the angular momentum, is the inertia tensor matrix of the inter-arm rotating joint, is the inertia tensor matrix of the first arm end rotating joint, is the inertia tensor moment of the robotic arm end effector, are the angular velocities of the corresponding components respectively;

[0103] Establish the inertia matrix of the robotic arm end effector coordinate system to the inter-arm rotating joint coordinate system.

[0104] Figure 2 Figure Figure 2 shows a schematic diagram of a robotic arm dynamics model provided by an embodiment of the present application. Taking a 6-axis robotic arm as an example to establish a dynamics model, it should be noted that the present application does not limit the specific number of robotic arm axes.

[0105] Preferably, when establishing the dynamics model of the robotic arm, the present invention establishes a robotic arm model based on a parallel structure. This model can move in two rotations and one translation in space, providing sufficient degrees of freedom for grasping operations. The dynamic equation of the robotic arm system can be expressed as: .

[0106] Furthermore, the present invention establishes a vector representation from the center of mass of the robotic arm to the center of the end effector of the robotic arm to accurately describe the system geometric relationship. The angular momentum H of the robotic arm can be expressed as: .

[0107] Establish the inertia matrix of the robotic arm end effector coordinate system to the inter-arm rotating joint coordinate system to describe the change of the inertia of the robotic arm during movement. Through coordinate transformation and matrix operation, the inertia under the end effector coordinate system is converted to the inter-arm rotating joint coordinate system.

[0108] In this embodiment, by establishing the generalized coordinates, dynamic model, angular momentum, and moment of inertia matrix of the robotic arm, a solid foundation is provided for subsequent contact state analysis. Through the accurate dynamic model, the dynamic responses of the robotic arm during the grasping of an object with a non-fixed posture can be accurately calculated, including position, velocity, acceleration, and contact force, etc. This helps to achieve precise control and safe implementation of the robotic arm, and improve the success rate and stability of the grasping task.

[0109] According to the above embodiment, in a specific implementation, the end of the robotic arm is represented as a combination of m polyhedrons, and the object with a non-fixed posture is represented as a combination of n polyhedrons, including:

[0110] The actuator at the end of the robotic arm is divided into m polyhedrons, where m≥2;

[0111] The m polyhedrons into which the actuator at the end of the robotic arm is divided are represented as a set V, , where, represents the j-th polyhedron corresponding to the actuator at the end of the robotic arm, ;

[0112] The object with a non-fixed posture is divided into n polyhedrons, where n≥2;

[0113] The n polyhedrons into which the object with a non-fixed posture is divided are represented as a set , , where, represents the i-th polyhedron corresponding to the object with a non-fixed posture, .

[0114] Figure 3 FIG. is a schematic diagram of the polyhedron representation of the end effector of the robotic arm provided by the embodiment of the present application, Figure 4 FIG. is a schematic diagram of the polyhedron representation of the object with a non-fixed posture provided by the embodiment of the present application. As shown in FIGS. Figure 3 and 4 , in this embodiment, the actuator at the end of the robotic arm is represented as a combination of m polyhedrons, and at the same time, the object with a non-fixed posture is represented as a combination of n polyhedrons, where m≥2 and n≥2.

[0115] Define the set of n polyhedrons as represents the n-th polyhedron corresponding to the object with a non-fixed posture, and the corresponding edge is Define the set of polyhedrons as represents the m-th polyhedron corresponding to the actuator at the end of the robotic arm, and the corresponding edge is . Exemplarily, Figure 2 in, The first polyhedron representing the end effector of the robot arm: the end effector body, The second polyhedron representing the end effector of the robot arm: the left gripper assembly, The third polyhedron representing the end effector partition of the robotic arm: the right gripper assembly. Figure 3 middle, The first polyhedron representing the division of non-fixed attitude objects: the satellite body; The second and third polyhedrons representing the division of non-fixed posture objects are both solar panels; The fourth polyhedron representing the partition of the non-fixed attitude object: the antenna assembly.

[0116] Compared with traditional point models or sphere models, polyhedron representation can more accurately describe complex geometric shapes and improve the accuracy of contact analysis.

[0117] According to the above embodiment, in a specific implementation scheme, judging in sequence whether each polyhedron corresponding to the robotic arm is in contact with any polyhedron corresponding to the non-fixed posture object according to the real-time coordinates of the robotic arm and the non-fixed posture object includes:

[0118] Based on the real-time coordinates of the robot arm and the non-fixed posture object, the edge feature vectors of each polyhedron corresponding to the robot arm and each polyhedron corresponding to the non-fixed posture object are determined, wherein the polyhedron No. The vector corresponding to the edge is represented as the eigenvector , then the set of feature vectors of all edges corresponding to the m polyhedrons divided by the actuator at the end of the robotic arm is ,polyhedron The vector corresponding to the lth edge of , then the set of feature vectors of all edges corresponding to the n polyhedrons divided by the non-fixed posture object is ;

[0119] judge Whether the number of intersection items is 0;

[0120] If not, it is determined that each polyhedron corresponding to the robot arm is in contact with any polyhedron corresponding to the non-fixed posture object;

[0121] If so, it is determined that each polyhedron corresponding to the robot arm is not in contact with any polyhedron corresponding to the non-fixed posture object.

[0122] For polyhedrons and , considering the position of the center point of the polyhedron and the vectors of all the edges of the polyhedron, the edge eigenvectors can be calculated. The vector corresponding to the kth edge of ; The vector corresponding to the l-th edge of the polyhedron is represented as the eigenvector . .

[0123] Considering all the edges of the two polyhedrons, the edges where the two polyhedrons are in contact are represented as follows:

[0124] ;

[0125] Among them, is the eigenvector corresponding to all the edges of the polyhedron , is the eigenvector corresponding to all the edges of the polyhedron .

[0126] When the edge eigenvectors of the two polyhedrons are the same, it corresponds to the edge contact of the two polyhedrons. It is defined whether the two polyhedrons are in contact by whether it is included. If the intersection is 0, the number of non-zero terms is used as the determination condition for whether the two polyhedrons are in contact.

[0127] Preferably, in the process of contact detection of the present invention, preliminary judgment can be made by calculating the distance between the vertices of the polyhedrons first.

[0128] Before judging whether the number of intersection terms is 0, it also includes:

[0129] Judging whether contact occurs according to the distance from any vertex of any polyhedron of the robotic arm to any edge of any polyhedron of the non-fixed posture object or the distance from any vertex of any polyhedron of the non-fixed posture object to any edge of any polyhedron of the robotic arm;

[0130] When the two polyhedrons are in contact, the sign function is used to represent the contact state:

[0131] .

[0132] In this embodiment, any polyhedron of the robotic arm is represented as A and any polyhedron of the target non-fixed posture object is represented as B. The vertex of A is , and the vertex of B is . Calculate the perpendicular distance from to the straight line :

[0133] ;

[0134] Similarly, calculate the perpendicular distance from to the straight line . If the distance , it indicates that the straight line and the straight line coincide, and the polyhedron A comes into contact with the target polyhedron B. If , then further calculate the intersection point .

[0135] When two polyhedrons come into contact, the sign function is used to represent the contact state. The introduction of this sign function enables the present invention to accurately distinguish different types of contact situations, thereby calculating the contact force and contact response more precisely. For example, when , it indicates that the two polyhedrons are in contact in the same direction, and the contact force is mainly along the normal direction. For example, both edges point outward or both point inward, which usually means that the two polyhedrons are in contact in the same direction, and the contact force is mainly along the normal direction; when , it indicates that the two polyhedrons are in contact in the opposite direction, and the contact force will have a large tangential component. For example, one edge points outward while the other points inward, which means that the two polyhedrons are in contact in the opposite direction, and the contact force will have a large tangential component; when , it indicates a special contact situation, and the calculation of the contact force needs to be specially processed. This situation refers to a special contact state where the edge directions are the same but the acting directions are opposite, and the calculation of the contact force needs to be specially processed.

[0136] At the edge where two polyhedrons are in contact, there are intersection points between the two contacting polyhedrons, and these intersection points can be represented by vectors. Specifically, when two polyhedrons are in contact, four vectors can be determined to uniquely determine the intersection point coordinates of the two contacting polyhedrons. Together with the three vertex coordinates of the two contacting polyhedrons, these four vectors can represent the intersection point coordinates of the edges of the two polyhedrons.

[0137] In practical applications, the present invention uses a threshold to determine whether a polyhedron is in contact. For example, when the distance between two vertices is less than a preset threshold (such as 10 mm), it is considered that contact has occurred. The selection of this threshold is based on the size and operating accuracy of the robotic arm. For a large robotic arm, a larger threshold (such as 20 - 30 mm) may need to be set to accommodate its operating error.

[0138] According to the above embodiments, in a specific implementation, obtaining the contact force at the contact point according to a preset non - linear damping model includes:

[0139] Defining two contacting polyhedrons and the polyhedron through a non - linear damping model, and obtaining the energy loss formula during the contact process of the two polyhedrons;

[0140] Taking the derivative of the energy loss formula to obtain the damping coefficient;

[0141] The contact force is obtained according to the damping coefficient and the contact force calculation formula;

[0142] The contact force calculation formula is: ;

[0143] Wherein, represents the l-th edge of the i-th polyhedron corresponding to the non-fixed attitude object, are respectively the normal vector, the tangent vector and the binormal vector corresponding to the edge , are respectively the corresponding damping coefficients, represents the contact collision force of the edge .

[0144] Figure 5 FIG. is a schematic diagram of polyhedron contact detection and intersection point determination provided by an embodiment of the present application; Figure 6 FIG. is an energy loss curve diagram of a non-linear damping model provided by an embodiment of the present application; Figure 7 FIG. is a contact force calculation flow chart provided by an embodiment of the present application; As Figure 5 , 6 , 7 shows, this embodiment adopts a non-linear damping model, and defines two polyhedrons in contact and polyhedron , and uses the following vector to represent the decomposition of the contact force: ;

[0145] Wherein, is the damping coefficient, is the sign function, are respectively the unit vectors corresponding to the vectors and the included angles, .

[0146] Preferably, the selection of the damping coefficient in the present invention depends on the material properties and the contact speed. For a typical end effector of a robotic arm (usually made of aluminum alloy or composite material), has a value range of 80-120 N-s / m, has a value range of 30-70 N-s / m, has a value range of 40-90 N-s / m. These parameter values are empirical values obtained based on a large number of simulation experiments and actual tests, and can better simulate the contact characteristics in the space environment.

[0147] During the contact process of the two polyhedrons, the energy loss formula is:

[0148] ;

[0149] Wherein, is the energy loss generated during the contact process, is a polyhedron is the contact edge of the polyhedron , is the contact force is the contact point velocity. The integration interval represents the start and end times of the contact

[0150] is obtained by differentiating the energy loss formula ;

[0151] where is the first derivative of the energy loss, representing the energy dissipation rate during the contact process. In this formula, x represents the contact state parameter, which can be: the displacement of the contact point (unit: m); the penetration depth between the polyhedrons (unit: m); the deformation of the contact area (unit: m);

[0152] According to different contact situations, x represents different physical quantities. In the current embodiment, x mainly represents the deformation during the contact process, which is directly related to the magnitude and direction of the contact force. This expression is one of the key innovations of the present invention, which directly correlates the contact force with the velocity, making the calculation of energy loss more accurate

[0153] The contact force between two contacting polyhedrons and is as follows :

[0154] ;

[0155] where represents the l-th edge of the i-th polyhedron corresponding to the non-fixed attitude object in contact, are the normal vector, tangent vector, and binormal vector corresponding to the edge respectively, are the corresponding damping coefficients respectively, represents the contact collision force of the edge

[0156] According to the above embodiment, in a specific implementation, it further includes

[0157] selecting the corresponding preset elastic coefficient according to the robotic arm and the non-fixed attitude object

[0158] determining the non-linear damping contact force according to the elastic coefficient

[0159] In this embodiment, the non-linear damping contact force model can be expressed as

[0160] ;

[0161] where​ is the elastic coefficient, is the parameter of the linear damping matrix, is the normal vector, is the tangential vector, is the angle between the normal vector and the tangential vector. In different contact cases, the damping coefficient takes different values:

[0162] When the contact is relatively slight (the deformation is less than 2 mm), ;

[0163] When the contact is medium (the deformation is between 2 - 5 mm), ;

[0164] When the contact is severe (the deformation is greater than 5 mm), .

[0165] By the method of setting the damping coefficient in segments, the material response under different degrees of contact can be simulated more precisely, improving the physical authenticity of the model.

[0166] According to the above embodiments, in a specific implementation, the contact force is analyzed according to the kinetic model to obtain the contact state response, including:

[0167] The first rotation equation of the end effector of the robotic arm is obtained through a preset moment of momentum formula;

[0168] The contact force between the end effector of the robotic arm and the edge of the non-fixed attitude object is obtained according to the contact force, contact acceleration at the contact point and the first rotation equation;

[0169] The second rotation equation representing the non-fixed attitude object is established;

[0170] The contact constraint condition of the non-fixed attitude object is obtained according to the contact force;

[0171] The contact differential equation is solved by the fourth-order Runge-Kutta method to obtain the contact response during the grasping process;

[0172] The contact differential equation is: ;

[0173] where h is the time step, are the coefficients of the Runge-Kutta method, representing the slopes at different moments respectively, w represents the time step index, corresponding to the w-th step of the simulation, y is the system state variable, which can be position, velocity, angle or angular velocity, etc. It is a vector containing all the variables required to describe the complete state of the system. In our application, y usually represents the combined state vector of the robotic arm joint angles and the position of the non-fixed attitude object.

[0174] Figure 8A contact response calculation flowchart provided by an embodiment of the present application is as follows Figure 8 as shown:

[0175] (1) During the contact response process, the rotation equation of the end effector of the robotic arm is obtained using the angular momentum formula:

[0176] ;

[0177] where represents the angular momentum of the robotic arm in the generalized coordinate q (unit: kg·m² / s), is the torque of the angular momentum in the direction of the q coordinate axis, are respectively the joint velocity and acceleration of the joint velocity in the direction of the q coordinate axis.

[0178] Preferably, the present invention considers that in the robotic arm base coordinate system to the end effector coordinate system of the robotic arm, the joint angles are respectively to , then the joint torque of the angular momentum under the coordinate axis is:

[0179] ;

[0180] where are respectively the joint torques of joint 2 and joint 6 in the direction of the q coordinate axis, are respectively the joint velocities of joint 2 and joint 6, are respectively the moments of inertia of joint 2 and joint 6, and the typical values are 2.5 kg·m² and 1.8 kg·m² respectively.

[0181] (2) Using the contact force and contact acceleration of the polyhedron, the rotation equation of the end effector of the robotic arm obtained by considering the angular momentum formula. After obtaining the contact force of each side of the non-fixed attitude object, the damping coefficient of each side of the non-fixed attitude object is used to represent it, and the contact force between the end effector of the robotic arm and the side of the non-fixed attitude object is expressed as:

[0182] ;

[0183] where are respectively the contact velocity and contact acceleration between the end effector of the robotic arm and the corresponding side of the non-fixed attitude object, is the displacement, are respectively the damping coefficients between the end effector of the robotic arm and the corresponding side of the non-fixed attitude object.

[0184] In practical applications, the present invention sets recommended damping coefficient values for different materials and contact situations. For example, for the contact between the end effector of a robotic arm made of aluminum alloy and a non-fixed attitude metal object, ; for the contact between an actuator made of composite material and a metal target, . These parameter values are obtained through a large number of experimental verifications, which can improve the calculation efficiency while ensuring the calculation accuracy.

[0185] (3) Use the rotation equation representing the non-fixed attitude object, expressed as the velocity vector of the joint rotation coordinates:

[0186] ;

[0187] Among them, are respectively the translation vector and velocity from the centroid of the non-fixed attitude object to the rotation joint of the non-fixed attitude object, is the angular velocity of the rotation joint of the non-fixed attitude object. This equation correlates the dynamic characteristics of the non-fixed attitude object with its dynamic model and is the basis for accurately calculating the contact response in the present invention.

[0188] (4) Considering the contact process, when the edges of two polyhedrons are the same and in contact, expand the contact force at the contact position of the polyhedron to obtain the contact constraint conditions of the non-fixed attitude object. The present invention introduces a contact determination threshold. When the distance between two edges is less than this threshold (usually set to 1 - 5 mm), it is considered that contact has occurred and the contact force is calculated.

[0189] (5) According to the contact constraint of the non-fixed attitude object, transform the contact force into the rotation equation of the non-fixed attitude object, and obtain the rotation equation of the non-fixed attitude object as:

[0190] ;

[0191] Among them, is the moment of inertia of the non-fixed attitude object, is the angular acceleration of the non-fixed attitude object, is the vector from the centroid of the non-fixed attitude object to the contact point, F is the contact force, is the contact moment of the corresponding edge of the non-fixed attitude object.

[0192] Pair and transform the contact moment with the position vector, which can be expressed as:

[0193] ;

[0194] Among them, is the translation vector from the centroid of the non-fixed attitude object to the rotation joint of the non-fixed attitude object, and A represents the vector transformation matrix corresponding to the edge.

[0195] Furthermore, the present invention innovatively introduces the concept of configuration pairs. By considering all contact constraints, the configuration pairs of non-fixed attitude objects are obtained:

[0196] ;

[0197] wherein, represents all configuration pairs, is the configuration matrix, which contains position, velocity, and acceleration information. This configuration pair method enables complex multi-point contact problems to be efficiently solved through matrix operations.

[0198] (6) Considering all contact constraint conditions, the contact forces considered by the end effector of the robotic arm are transformed into configuration pairs. The end configuration pairs of the non-fixed attitude object after considering contact are expressed as:

[0199] ;

[0200] wherein, is the position vector, is the direction vector, is the distance parameter, is the linear velocity, is the angular velocity.

[0201] (7) The contact response during the grasping process is obtained by solving the above contact differential equation. The present invention uses the fourth-order Runge-Kutta method for numerical solution, and its formula is:

[0202] ;

[0203] wherein, h is the time step, are the coefficients of the Runge-Kutta method, representing the slopes at different times respectively. w represents the time step index, corresponding to the w-th step of the simulation, and y is the system state variable.

[0204] ;

[0205] ;

[0206] ;

[0207] ;

[0208] Through this method, the present invention can accurately calculate the changes in position, velocity, and acceleration during the contact process, providing accurate dynamic parameters for subsequent grasping control.

[0209] In a specific embodiment, Figure 9 is the simulation result diagram of the contact force varying with time in the embodiment of the present application; Figure 10This is the position trajectory simulation result diagram of the process of the robotic arm grasping an object with a non-fixed posture in the embodiment of the present application. As Figure 9 and Figure 10 shown, the number of joints of the robotic arm is set to 7 degrees of freedom, the joint angle range is [0°, 180°], the mass is 100 Kg, the initial velocity and the initial length are both set to zero, the motor torque is 35 N, the damping coefficient is 75 N / s, the simulation step size is 0.01, and the joint length of the polyhedron is 500 mm. Through the simulation analysis of different damping coefficients, a series of comparative tests were carried out in the present invention. When the damping coefficient is set to 75 N / s, the contact force between the robotic arm and the object with a non-fixed posture reaches a peak of about 120 N at about 0.02 seconds after the contact starts, and then gradually decays to 0 within 0.15 seconds. Compared with the traditional spherical model, the polyhedron contact model of the present invention can more accurately reflect the change process of the contact force. Especially in the force growth stage at the initial stage of contact, the traditional model often underestimates the contact force by about 15 - 20%. At the same time, by changing the damping coefficient (such as setting it to 50 N / s or 100 N / s), the contact response under different material characteristics can be simulated to meet the requirements of different application scenarios.

[0210] Figure 10 shows the position trajectory of the robotic arm during the process of grasping an object with a non-fixed posture. Through the method of the present invention, the robotic arm can quickly adjust its position after contact and complete the stable grasping of the target within about 0.5 seconds. Compared with the traditional method, the grasping success rate of the present invention is increased by about 25%. Especially for non-fixed posture objects with complex shapes and large moments of inertia, the advantage is more obvious.

[0211] In the above embodiment, the contact analysis method for the robotic arm to grasp an object with a non-fixed posture is described in detail. The present application also provides an embodiment corresponding to the contact analysis device for the robotic arm to grasp an object with a non-fixed posture. It should be noted that the present application describes the embodiment of the device part from two perspectives, one is from the perspective of functional modules, and the other is from the perspective of hardware.

[0212] From the perspective of functional modules, Figure 11 This is the structural diagram of a contact analysis device for a robotic arm to grasp an object with a non-fixed posture provided in the embodiment of the present application. As Figure 11 shown, a contact analysis device for a robotic arm to grasp an object with a non-fixed posture includes:

[0213] A preset module 21, configured to obtain the dynamic model of the robotic arm established based on the operating environment;

[0214] A simulation module 22, configured to represent the end of the robotic arm as a combination of m polyhedrons, and represent the object with a non-fixed posture as a combination of n polyhedrons, where m and n are positive integers greater than 1;

[0215] A judgment module 23, configured to sequentially judge whether each polyhedron corresponding to the robotic arm contacts any one of the polyhedrons corresponding to the non-fixed attitude object according to the real-time coordinates of the robotic arm and the non-fixed attitude object; if there is contact, trigger the contact response module 24;

[0216] A contact response module 24, configured to obtain the contact point of contact between the two polyhedrons;

[0217] A contact force calculation module 25, configured to obtain the contact force at the contact point according to a preset non-linear damping model;

[0218] An analysis module 26, configured to analyze the contact force according to a dynamics model to obtain a contact state response.

[0219] Since the embodiments of the device part correspond to the embodiments of the method part, for the embodiments of the device part, please refer to the description of the embodiments of the method part, which will not be elaborated here.

[0220] Figure 12 As shown in the structural diagram of another contact analysis device for a robotic arm to grasp a non-fixed attitude object provided by an embodiment of the present application, Figure 12 A contact analysis device for a robotic arm to grasp a non-fixed attitude object includes: a memory 30, configured to store a computer program;

[0221] A processor 31, configured to implement the steps of the method for obtaining user operation habit information in the above-mentioned embodiment (the contact analysis method for a robotic arm to grasp a non-fixed attitude object) when executing the computer program.

[0222] The contact analysis device for a robotic arm to grasp a non-fixed attitude object provided in this embodiment may include, but is not limited to, a mobile terminal, a personal computer, a workstation, etc.

[0223] Among them, the processor 31 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 31 may be implemented in at least one hardware form of a digital signal processor (DSP), a field-programmable gate array (FPGA), or a programmable logic array (PLA). The processor 31 may also include a main processor and a coprocessor. The main processor is a processor used to process data in the wake state, also known as the central processing unit (CPU); the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, the processor 31 may be integrated with a graphics processing unit (GPU), and the GPU is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor 31 may further include an artificial intelligence (AI) processor, and the AI processor is used to process computational operations related to machine learning.

[0224] The memory 30 may include one or more computer-readable storage media, and the computer-readable storage media may be non-transitory. The memory 30 may further include high-speed random access memory and non-volatile memory, such as one or more disk storage devices and flash storage devices. In this embodiment, the memory 30 is at least used to store the following computer program 301. After the computer program is loaded and executed by the processor 31, it can implement the relevant steps of the contact analysis method for the robotic arm to grasp an object with a non-fixed posture disclosed in any of the foregoing embodiments. In addition, the resources stored in the memory 30 may further include an operating system 302 and data 303, etc., and the storage method may be transient storage or permanent storage. Among them, the operating system 302 may include Windows, Unix, Linux, etc. The data 303 may include, but is not limited to, the data involved in implementing the contact analysis method for the robotic arm to grasp an object with a non-fixed posture.

[0225] In some embodiments, the contact analysis device for the robotic arm to grasp an object with a non-fixed posture may further include a display screen 32, an input / output interface 33, a communication interface 34, a power supply 35, and a communication bus 36.

[0226] Those skilled in the art can understand that Figure 12 the structure shown in

[0227] The contact analysis device for a robotic arm to grasp an object with a non-fixed posture provided by an embodiment of the present application includes a memory and a processor. When the processor executes the program stored in the memory, the following method can be implemented: a contact analysis method for a robotic arm to grasp an object with a non-fixed posture.

[0228] Finally, the present application also provides an embodiment corresponding to a computer-readable storage medium. A computer program is stored on the computer-readable storage medium. When the computer program is executed by the processor, the steps recorded in the contact analysis method embodiment for a robotic arm to grasp an object with a non-fixed posture as described above are implemented.

[0229] It can be understood that if the method in the above embodiments is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and executes all or part of the steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical discs that can store program codes.

[0230] The computer-readable storage medium provided in this embodiment stores a computer program. When the processor executes this program, the following method can be implemented: a contact analysis method for a robotic arm to grasp an object with a non-fixed posture.

[0231] The contact analysis method, device, and medium for a robotic arm to grasp an object with a non-fixed posture provided by the present application are introduced in detail above. The embodiments in the specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple. For the relevant parts, refer to the description of the method part. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

[0232] It should also be noted that in this specification, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

Claims

1. A contact analysis method for a robot arm grasping an object with a non-fixed posture, characterized in that: include: Obtain the dynamic model of the robot arm based on the operating environment; The end of the robot arm is represented as a combination of m polyhedrons, and the non-fixed posture object is represented as a combination of n polyhedrons, where m and n are positive integers greater than 1; Determining in sequence whether each polyhedron corresponding to the robotic arm is in contact with any polyhedron corresponding to the non-fixed posture object according to the real-time coordinates of the robotic arm and the non-fixed posture object; If they are in contact, obtain the contact points where the two polyhedrons are in contact; Obtaining the contact force of the contact point according to a preset nonlinear damping model; The contact force is analyzed according to the dynamic model to obtain a contact state response.

2. The contact analysis method for a robot arm grasping an object with a non-fixed posture according to claim 1, characterized in that: The steps to establish the dynamic model of the robotic arm are as follows: Establishing the generalized coordinates of the robot with a 6-axis robot , where q1 and q2 are the joint angles from the base coordinate system to the inter-arm rotation joint, q3 and q4 are the joint angles from the inter-arm rotation joint to the first arm end rotation joint, and q5 and q6 are the joint angles from the first arm end rotation joint to the end tool rotation joint; Construct a kinetic model based on the kinetic equation; The kinetic equation is: ; Where M is the mass matrix, C is the constraint matrix, G is the gravity matrix, and T is the Coriolis matrix. is the linear damping matrix, , is the control input, is the acceleration vector, is the velocity vector; Establish the momentum from the center of mass of the robot to the center of the end effector of the robot; The angular momentum is expressed as: ; In the formula, represents the momentum, is the inertia tensor matrix of the inter-arm revolute joint, is the inertia tensor matrix of the first arm end revolute joint, is the inertia tensor moment of the robot end effector, are the angular velocities of the corresponding components respectively; Establish the moment of inertia matrix from the robot end effector coordinate system to the inter-arm rotation joint coordinate system.

3. The contact analysis method for a robot arm grasping an object with a non-fixed posture according to claim 2, characterized in that: The end of the robot arm is represented as a combination of m polyhedrons, and the non-fixed posture object is represented as a combination of n polyhedrons, including: Divide the actuator at the end of the robot arm into m polyhedrons, where m ≥ 2; The m polyhedrons divided by the actuator at the end of the robot arm are represented as a set V, ,in, represents the jth polyhedron corresponding to the actuator at the end of the robotic arm, ; Divide the non-fixed posture object into n polyhedrons, where n ≥ 2; The n polyhedrons divided into non-fixed posture objects are represented as a set , ,in, represents the i-th polyhedron corresponding to the non-fixed posture object, .

4. The contact analysis method for a robot arm grasping an object with a non-fixed posture according to claim 3, characterized in that: According to the real-time coordinates of the robotic arm and the non-fixed posture object, it is sequentially determined whether each polyhedron corresponding to the robotic arm is in contact with any polyhedron corresponding to the non-fixed posture object, including: The edge feature vectors of each polyhedron corresponding to the robotic arm and each polyhedron corresponding to the non-fixed posture object are determined based on the real-time coordinates of the robotic arm and the non-fixed posture object, wherein the polyhedron No. The vector corresponding to the edge is represented as the eigenvector , then the set of feature vectors of all edges corresponding to the m polyhedrons divided by the actuator at the end of the robotic arm is ,polyhedron The vector corresponding to the lth edge of , then the set of feature vectors of all edges corresponding to the n polyhedrons divided by the non-fixed posture object is ; judge Whether the number of intersection items is 0; If not, determining that each polyhedron corresponding to the robotic arm is in contact with any polyhedron corresponding to the non-fixed posture object; If so, it is determined that each polyhedron corresponding to the robotic arm is not in contact with any polyhedron corresponding to the non-fixed posture object.

5. The contact analysis method for a robot arm grasping an object with a non-fixed posture according to claim 4, characterized in that: The step of obtaining the contact force of the contact point according to a preset nonlinear damping model includes: Define two polyhedrons in contact using a nonlinear damping model and polyhedron , and obtain the energy loss formula during the contact process between two polyhedrons; Derivatively obtaining a damping coefficient by taking the energy loss formula; Obtaining the contact force according to the damping coefficient and the contact force calculation formula; The contact force calculation formula is: ; in, represents the lth edge of the ith polyhedron corresponding to the non-fixed posture object, Side The corresponding normal vector, tangent vector and binormal vector, are the corresponding damping coefficients, Represents edge contact collision force.

6. The contact analysis method for a robot arm grasping an object with a non-fixed posture according to claim 5, characterized in that: The step of analyzing the contact force according to the dynamic model to obtain a contact state response includes: The first rotation equation of the end effector of the robot arm is obtained by presetting the momentum formula; According to the contact force and contact acceleration of the contact point and the first rotation equation, the contact force between the end effector of the robot arm and the edge of the non-fixed posture object is obtained; Establishing a second rotation equation representing the non-fixed posture object; Obtaining contact constraint conditions of the non-fixed posture object according to the contact force; The contact differential equation is solved by the fourth-order Runge-Kutta method to obtain the contact response during the grasping process. The contact differential equation is: ; Where h is the time step, are the coefficients of the Runge-Kutta method, representing the slopes at different times, w represents the time step index, corresponding to the wth step of the simulation, and y is the system state variable.

7. The contact analysis method for a robot arm grasping an object with a non-fixed posture according to claim 5, characterized in that: Also includes: Selecting a corresponding preset elastic coefficient according to the robotic arm and the non-fixed posture object; A nonlinear damping contact force is determined based on the elastic coefficient.

8. A contact analysis device for a robot arm grasping an object with a non-fixed posture, characterized in that: include: A preset module is used to obtain the dynamic model of the robot arm based on the operating environment; A simulation module, used to represent the end of the robot arm as a combination of m polyhedrons, and represent the non-fixed posture object as a combination of n polyhedrons, where m and n are positive integers greater than 1; A judgment module, used for judging in sequence whether each polyhedron corresponding to the robotic arm is in contact with any polyhedron corresponding to the non-fixed posture object according to the real-time coordinates of the robotic arm and the non-fixed posture object; if so, triggering a contact response module; The contact response module is used to obtain the contact points of two polyhedrons; A contact force calculation module, used for obtaining the contact force of the contact point according to a preset nonlinear damping model; The analysis module is used to analyze the contact force according to the dynamic model to obtain a contact state response.

9. A contact analysis device for a robot arm grasping an object with a non-fixed posture, characterized in that: include: Memory for storing computer programs; A processor is used to implement the steps of the contact analysis method for a robot arm grasping an object with a non-fixed posture as described in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the contact analysis method for a robot arm grasping an object with a non-fixed posture as described in any one of claims 1 to 7 are implemented.

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