Pose compensation method and system for end effector of heavy-load mechanical arm

Abstract

The invention relates to a pose compensation method and system for an end effector of a heavy-load mechanical arm. The pose compensation method comprises the following steps: respectively constructing finite element models for a plurality of connecting rod units forming the mechanical arm; solving each finite element model to obtain deformation of the load end under different stress and rod length, and constructing a mapping model of the corresponding deformation of each connecting rod unit under different stress according to the deformation; calculating the actual stress of each connecting rod unit based on the actual load of the actuator and the structural parameters of the connecting rod; calculating the deformation of the connecting rod corresponding to each connecting rod unit through a mapping model of the deformation and the actual stress; according to the forward kinematics homogeneous transformation matrix, the offset of the end effector caused by the deformation of each connecting rod when each connecting rod deforms independently is obtained; and the offsets of all the actuators are accumulated, the compensation amount used for pose compensation of the end effector is generated, pose compensation of the end effector of the mechanical arm is achieved, and the working efficiency and accuracy of the mechanical arm are improved.

Description

Technical Field

[0001] The invention relates to a posture compensation method and system for a heavy-loaded mechanical arm end effector, belonging to the technical field of mechanical arm control. Background Art

[0002] In modern machinery manufacturing or mechanical equipment operation, heavy-duty mechanical arms are often used to carry or install large mechanical parts, such as liners, drive shafts and gears of large mills. The liners of large mills are heavy and can weigh several tons. It is difficult to ensure the installation accuracy of the liners by manual disassembly, transportation and installation of mill liners, and the labor intensity is high. When using a mechanical arm for operation, the workload at the end of the mechanical arm is extremely large due to the influence of the liners' own weight.

[0003] At the same time, during the operation, the robot arm needs to install or remove the liner through different arm span configurations. Due to its large size and weight, the structural parts are deformed, causing the position of the end of the robot arm to change by hundreds of millimeters. Therefore, in the actual operation of the heavy robot arm, if the end effector is not corrected and compensated, it is difficult to meet the requirements of rapid installation and removal of the mill liner. Summary of the invention

[0004] The purpose of the present invention is to provide a posture compensation method and system for the end effector of a heavy-duty mechanical arm, so as to realize posture correction compensation of the end effector of the heavy-duty mechanical arm and improve the operating efficiency and accuracy of the heavy-duty mechanical arm.

[0005] To achieve the above object, on the one hand, the present invention proposes a posture compensation method for a heavy-duty robot end effector, performing the following steps:

[0006] 1) Construct finite element models for several connecting rod units that make up the robotic arm respectively;

[0007] 2) Solving each finite element model to obtain the deformation of the load end under different forces and rod lengths, and constructing a mapping model of the corresponding deformation of each connecting rod unit under different forces according to the deformation;

[0008] 3) Based on the actual load of the end effector and the structural parameters of the connecting rod, the actual force of each connecting rod unit is calculated using the force Jacobian matrix;

[0009] 4) For each connecting rod unit, the deformation of the connecting rod is calculated through the deformation mapping model and the actual force;

[0010] 5) According to the forward kinematics homogeneous transformation matrix, the deformation of each link is input into the homogeneous transformation matrix to obtain the end effector offset caused by the deformation of each link when the link is deformed individually; all actuator offsets are accumulated to generate the compensation for the end effector posture compensation.

[0011] Furthermore, the finite element model is constructed through the following steps:

[0012] Decompose the robot arm into several link units according to the robot arm joints;

[0013] According to the working space range of the robot arm and the activity limit of each robot arm joint, a finite element static analysis task table is established for all link units in different posture states; the finite element static analysis task table is used as the basis for each link unit, combined with the robot arm three-dimensional digital model and static analysis module, and a finite element model is generated through model simplification, unit discretization, meshing and boundary load definition.

[0014] Furthermore, the task table includes connecting rod length parameters and connecting rod loads, so as to be used for calculating the deformation of the connecting rod load end under different forces in step 2).

[0015] Furthermore, the actual force of the connecting rod unit is calculated by the following steps:

[0016] According to the velocity Jacobian matrix, the force Jacobian matrix of each link element is established;

[0017] Based on the actual load of the actuator and the force Jacobian matrix of all link units, the force mapping relationship between the end-effector force and the actual force of the link unit is established to obtain the actual force of each link unit.

[0018] Furthermore, the force mapping relationship is the following formula:

[0019]

[0020] Among them, τ i is the actual force of the i-th connecting rod unit; is the force Jacobian matrix of the i-th link unit; F is the actual load of the end effector.

[0021] Furthermore, F=(f x ,f y ,f z ,m x ,m y ,m z ), where f x , f y , f z Respectively represent the actual force of the end effector along the x, y, and z axes, m x , m y , m z Represent the actual moments about the x, y, and z axes respectively.

[0022] Furthermore, the deformation of the connecting rod is calculated by the following steps:

[0023] The connecting rod length and actual force of the connecting rod unit are taken as variables, the variable mapping model of the connecting rod unit is compared, and the connecting rod deformation of each connecting rod unit is calculated using the multi-dimensional interpolation method.

[0024] On the other hand, the present invention further proposes a posture compensation system for a heavy-loaded robot arm end effector, wherein the system is used to execute the posture compensation method for the heavy-loaded robot arm end effector as described above.

[0025] The beneficial effects of the present invention are as follows: finite element models are constructed for several connecting rod units that constitute the robotic arm respectively; each finite element model is solved to obtain the deformation of the load end under different forces and rod lengths, and a mapping model of the corresponding deformation of each connecting rod unit under different forces is constructed according to the deformation; based on the actual load of the actuator and the connecting rod structural parameters, the actual force of each connecting rod unit is calculated using the force Jacobian matrix; the deformation of the connecting rod is calculated for each connecting rod unit through the mapping model of the deformation and the actual force; according to the forward kinematics homogeneous transformation matrix, each connecting rod deformation is input into the homogeneous transformation matrix to obtain the end effector offset caused by the connecting rod deformation when each connecting rod is deformed individually; all actuator offsets are accumulated to generate a compensation amount for end effector posture compensation, so as to realize rapid feedback correction of each joint unit of the robotic arm and improve the operation efficiency and accuracy of the robotic arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of a posture compensation method for a heavy-duty manipulator end effector proposed by the present invention;

[0027] Figure 2 A schematic diagram of a heavy-duty robot arm joint structure in an actual application scenario of a posture compensation method for a heavy-duty robot arm end effector proposed by the present invention;

[0028] Figure 3 It is a flow chart of a posture compensation method for a heavy-duty manipulator end effector proposed by the present invention in an actual application scenario;

[0029] Reference numerals:

[0030] A-upper arm; B-lower arm; C-wrist; D-end effector;

[0031] 1- Frame. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0033] The inventive concept of the present invention is: in order to solve the problem of inaccurate posture of the end effector of the robot arm during actual operation, by decomposing the robot arm joints, modeling the deformation mapping, calculating the actual force of the connecting rod unit and accumulating the positive deformation, the posture compensation of the end effector of the robot arm can be calculated quickly, so as to achieve rapid feedback and correction of the operating parameters of each joint of the robot arm, thereby improving the operating efficiency and accuracy of the robot arm.

[0034] Method Example 1:

[0035] like Figure 1 FIG. 1 is a flow chart of a posture compensation method for a heavy-duty manipulator end effector proposed by the present invention, which includes step S11, step S12, step S13, step S14 and step S15. Specifically:

[0036] Step S11, constructing finite element models for the several link units that constitute the robotic arm respectively; here, the finite element model includes but is not limited to a finite element statics model, and the finite element statics model refers to a model that uses a finite element analysis method to simulate the mechanical behavior of a structure under a static load, so as to achieve a reasonable "disassembly" of the robotic arm, which becomes an important step in converting the posture compensation of the end effector into calculating the link deformation of each link unit.

[0037] It should be noted that the finite element model is constructed through the following steps: the robot arm is decomposed into several link units according to the robot arm joints, for example Figure 2 As shown, it is a schematic diagram of the joint structure of a heavy-duty robot arm in an actual application scenario of a posture compensation method for an end effector of a heavy-duty robot arm proposed by the present invention, wherein the robot arm is arranged on a frame 1, starting from the side of the robot arm connected to the frame, it is sequentially an upper arm A, a lower arm B, a wrist C and an end effector D, wherein the upper arm A is used for extension and retraction, the lower arm B is used for rotation, pitch and extension, and the wrist C is used for yaw, pitch and roll; when the robot arm is decomposed, it will be decomposed according to the upper arm A, the lower arm B and the wrist C.

[0038] According to the working space range of the robot arm and the activity limit of each robot arm joint, a finite element static analysis task table for all connecting rod units in different posture states is established; here, the task table includes the connecting rod length parameters and the load on the connecting rod, which is used to calculate the deformation of the connecting rod force end under different forces in step S12.

[0039] Each connecting rod unit is based on the finite element static analysis task table, combined with the three-dimensional digital model of the robotic arm and the statics analysis module, and a finite element model is generated through model simplification, unit discretization, meshing and boundary load definition. Among them, the statics analysis model includes but is not limited to the ANSYS statics analysis model.

[0040] Step S12, solve each finite element model to obtain the deformation of the load end under different forces and rod lengths, and construct a mapping model of the corresponding deformation of each connecting rod unit under different forces based on the deformation; here, in the actual application scenario, based on the finite element model including the connecting rod length parameters and the load on the connecting rod, the finite element solution of the deformation of the load-bearing end of the connecting rod under different forces is performed in an offline manner to obtain the deformation of each connecting rod unit under different forces, and a mapping model of the deformation of each connecting rod unit with respect to the connecting rod length parameters and the load on the connecting rod is established, so that the corresponding deformation data of the connecting rod units with various parameters can be obtained, the requirements of various connecting rod units can be met, and accurate data support is provided for the subsequent compensation calculation.

[0041] Step S13, based on the actual load of the end effector and the structural parameters of the connecting rod, the actual force of each connecting rod unit is calculated using the force Jacobian matrix. It should be noted that the actual force of the connecting rod unit is calculated by the following steps: the force Jacobian matrix of each connecting rod unit is established according to the velocity Jacobian matrix; here, the velocity Jacobian matrix refers to the matrix describing the relationship between the joint velocity and the end effector velocity; the force Jacobian matrix refers to the matrix describing the relationship between the joint force and the end effector force.

[0042] Based on the actual load of the actuator and the force Jacobian matrix of all the connecting rod units, a force mapping relationship between the force of the end effector and the actual force of the connecting rod unit is established to obtain the actual force of each connecting rod unit; specifically, the force mapping relationship is the following formula:

[0043]

[0044] Among them, τ i is the actual force of the i-th connecting rod unit; is the force Jacobian matrix of the i-th link unit; F is the actual load of the end effector; at the same time, F=(f x ,f y ,f z ,m x ,m y ,m z ), where f x , f y , f z Respectively represent the actual force of the end effector along the x, y, and z axes, m x , m y , m z Respectively represent the actual moments about the x, y, and z axes; Each column in can be obtained by the forward kinematics model, and i is the link unit index.

[0045] Step S14, corresponding to each connecting rod unit, the connecting rod deformation is calculated through the deformation mapping model and the actual force; here, for each connecting rod unit, the connecting rod length and the actual force of the connecting rod unit are used as variables, and the variable mapping model of the connecting rod unit is compared, and the connecting rod deformation of each connecting rod unit is calculated using a multidimensional interpolation method; it should be noted that the data of 7 dimensions (i.e., 3 dimensions of the actual force of the end effector along the x, y, and z axes, 3 dimensions of the actual torque of the end effector about the x, y, and z axes, and the connecting rod length dimension of the connecting rod unit) are integrated and calculated through the multidimensional interpolation method to obtain the final connecting rod deformation, thereby improving the accuracy of the connecting rod deformation.

[0046] Step S15, according to the forward kinematics homogeneous transformation matrix, input each link deformation into the homogeneous transformation matrix to obtain the end effector offset caused by the link deformation when each link deforms individually; accumulate all the actuator offsets to generate a compensation amount for end effector posture compensation.

[0047] Through the above steps S11 to S15, the finite element model is used to decompose the robot arm, and the deformation mapping model is constructed and the actual force is calculated to prepare data for the subsequent forward kinematics, so as to quickly and accurately calculate the posture compensation of the end effector, and directly solve the impact of the deviation of the end effector posture on the heavy-loaded robot arm.

[0048] In a preferred embodiment of the present invention, the robot arm is preferably decomposed into link unit 1-link unit N according to the robot arm joints, and a finite element model (i.e., M1, M2, ..., M (N-1) 、M N , where N is a positive integer greater than or equal to 1). i The deformation of the connecting rod unit i under different forces is calculated, and the deformation mapping model P of the connecting rod unit i is constructed according to the deformation of the connecting rod unit i under all forces. i ; Similarly, each link unit obtains its corresponding deformation mapping model through the above. Obtain the actual load of the end effector and the link length parameters of the N link units (the link structure parameters are preferably the link length parameters), call the force Jacobian matrix, establish the force mapping relationship between the end effector force and the actual force of the N link units, and obtain the actual force τ1, τ2, ..., τ of each link unit. (N-1) , τ N For the link unit i, the mapping model P of its deformation i and the actual force τ i , calculate the connecting rod deformation u of connecting rod unit i iSimilarly, the corresponding connecting rod deformation is calculated for each connecting rod unit. Based on forward kinematics, the deformation of each connecting rod u i Input into the homogeneous transformation matrix to obtain the deformation u of the connecting rod when the connecting rod i deforms alone i The corresponding end effector offset w i ; Accumulate all actuator offsets to generate the compensation amount W for end-effector posture compensation.

[0049] Method Example 2:

[0050] like Figure 3 The figure shows a flow chart of a posture compensation method for a heavy-duty robot end effector proposed by the present invention in an actual application scenario, wherein the first step is to decompose the robot joints and perform finite element modeling. Specifically, first, a local coordinate system of each joint is established, and the robot is decomposed into N connecting rod units with the coordinate origin as a reference, where N is the robot's degree of freedom. Secondly, a finite element static analysis task table of each connecting rod unit in a number of posture states is established based on the robot's workspace range and joint activity limits. The variables involved in the task table include the connecting rod length parameter J. im and the load F on the connecting rod in , where i = (1, 2, ..., N) is the link unit index; m and n are variable indexes, corresponding to different link lengths and load sizes. Finally, based on the analysis task table, combined with the three-dimensional digital model of the robotic arm and the ANSYS static analysis module, the corresponding models of different link units are established through model simplification, unit discretization, mesh division and boundary load definition, and several finite element static models M are obtained. i .

[0051] Step 2: Establish the mapping model P of the deformation of each connecting rod unit i Specifically, according to the finite element statics model established in the first step, the deformation of the connecting rod force end is solved by finite element in an offline manner to obtain the deformation of each connecting rod unit under different forces, and the deformation mapping model P of each connecting rod unit is established. i =f(J im ,F in ), where f is the mapping function determined by solving the finite element model, P i It is the deformation mapping model of the i-th link unit, which is used for the subsequent calculation of the posture compensation of the end effector of the robot arm.

[0052] Step 3: Calculate the actual load (i.e., actual force) of each link unit. Specifically, obtain the actual end effector load and connecting rod length parameter J im , according to the actual load of the end effector of the robot And the structural parameters of each connecting rod J imCalculate the actual force load of each link unit, where the force Jacobian matrix of each link unit is established according to the velocity Jacobian matrix Each column can be obtained by the forward kinematics model, and i is the index of the link unit. Thus, the force on the end effector and the force on each link unit τ are established. i The linear mapping relationship between:

[0053]

[0054] Among them, τ i is the actual force of the i-th connecting rod unit; is the force Jacobian matrix of the i-th link unit; F is the actual load of the end effector; F = (f x ,f y ,f z ,m x ,m y ,m z ), where f x , f y , f z Respectively represent the actual force of the end effector along the x, y, and z axes, m x , m y , m z Represents the actual torque about the x, y, and z axes respectively. τ i =(τ i1 ,τ i2 ,…,τ iN ) is the actual torque (rotational joint) or actual force (mobile joint) at each link unit of the robot. The static Jacobian matrix is ​​a mapping of the operation space to the joint space, so the actual force of each link unit can always be uniquely determined by the actual load of the end effector.

[0055] Step 4: Calculate the deformation of each connecting rod unit. Specifically, for each connecting rod unit, the deformation mapping model established in the second step and the actual force obtained in the third step are used as input to calculate the deformation of each connecting rod unit. The connecting rod length and the actual force are used as variables to compare the deformation mapping model P of the connecting rod. i , calculate the connecting rod deformation u of each connecting rod unit by multi-dimensional fast interpolation method i .

[0056] Step 5: Calculate the end effector posture compensation. Specifically, establish a local DH parameter coordinate system for each link unit of the robot arm, and calculate the homogeneous transformation matrix between each link. Obtain the expression of the end effector offset in the coordinate system of each link unit The connecting rod deformation u of each connecting rod calculated in the fourth step iAs input, it is recursively deduced from the base coordinates to the end effector, all actuator offsets are accumulated, and used as the posture compensation W for subsequent feedback control.

[0057] System Example:

[0058] On the other hand, the present invention also proposes a posture compensation system for a heavy-loaded robotic arm end effector, and the system is used to execute the posture compensation method for the heavy-loaded robotic arm end effector as described above. Here, the embodiment of the posture compensation system for the heavy-loaded robotic arm end effector please refer to the embodiment of the posture compensation method for the heavy-loaded robotic arm end effector described above, which will not be repeated here.

[0059] In summary, the present invention establishes several deformation mapping models for each connecting rod unit, and uses multi-dimensional interpolation to accurately calculate the actual force and deformation of each connecting rod, thereby obtaining the compensation amount of the end effector posture. This method can quickly calculate the posture compensation amount of the end effector of the robot arm according to the given working conditions, ensure the operation control accuracy and operation efficiency, and use the combination of finite element statics analysis and multi-dimensional interpolation fast calculation to quickly calculate the posture compensation amount.

Claims

1. A posture compensation method for a heavy-duty robot end effector, characterized in that: Follow these steps: 1) Construct finite element models for each of the connecting rod units that make up the robotic arm; 2) Solving each finite element model to obtain the deformation of the load end under different forces and rod lengths, and constructing a mapping model of the corresponding deformation of each connecting rod unit under different forces based on the deformation; 3) Based on the actual load of the end effector and the structural parameters of the connecting rod, the actual force of each connecting rod unit is calculated using the force Jacobian matrix; 4) For each connecting rod unit, the deformation of the connecting rod is calculated through the deformation mapping model and the actual force; 5) According to the forward kinematics homogeneous transformation matrix, the deformation of each link is input into the homogeneous transformation matrix to obtain the end effector offset caused by the deformation of each link when the link deforms alone; All actuator offsets are accumulated to generate compensation for end-effector pose compensation.

2. The posture compensation method of the heavy-duty robot arm end effector according to claim 1 is characterized in that: The finite element model is constructed by the following steps: Decompose the robot arm into several link units according to the robot arm joints; According to the working space range of the robot arm and the activity limit of each robot arm joint, a finite element static analysis task table is established for all link units in different posture states; the finite element static analysis task table is used as the basis for each link unit, combined with the robot arm three-dimensional digital model and static analysis module, and a finite element model is generated through model simplification, unit discretization, meshing and boundary load definition.

3. The posture compensation method of the heavy-duty robot arm end effector according to claim 2 is characterized in that: The task table includes the connecting rod length parameters and the load on the connecting rod, so as to be used for calculating the deformation of the connecting rod load end under different forces in step 2).

4. The posture compensation method of the heavy-duty robot arm end effector according to claim 1, characterized in that: The actual forces on the connecting rod unit are calculated by the following steps: According to the velocity Jacobian matrix, the force Jacobian matrix of each link element is established; Based on the actual load of the actuator and the force Jacobian matrix of all link units, the force mapping relationship between the end-effector force and the actual force of the link unit is established to obtain the actual force of each link unit.

5. The posture compensation method of the heavy-duty robot arm end effector according to claim 4, characterized in that: The force mapping relationship is as follows: in, is the actual force of the i-th connecting rod unit; is the force Jacobian matrix of the i-th link element; F is the actual load of the end effector.

6. The posture compensation method of the heavy-duty robot arm end effector according to claim 5, characterized in that: , where f x , f y , f z Respectively represent the actual force of the end effector along the x, y, and z axes, m x , m y , m z Represent the actual moments about the x, y, and z axes respectively.

7. The posture compensation method of the heavy-duty robot arm end effector according to claim 6, characterized in that: Calculate the connecting rod deformation by the following steps: The connecting rod length and actual force of the connecting rod unit are taken as variables, the variable mapping model of the connecting rod unit is compared, and the connecting rod deformation of each connecting rod unit is calculated using the multi-dimensional interpolation method.

8. A posture compensation system for a heavy-duty robot end effector, characterized in that: The system is used to perform the method as described in any one of claims 1 to 7.

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