CN108393928B - Multi-rigid body-finite element hybrid analysis method for contact collision of flexible robot manipulators - Google Patents

Abstract

The invention discloses a multi-rigid-finite element mixed analysis method for contact collision of a flexible robot mechanical arm, which utilizes an equivalent unit to simulate a hinge bolt and a spring in a finite element model; in the calculation process, when the mechanical arm is not in contact, the rigid body algorithm is adopted by the mechanical arm, and when the mechanical arm is in contact, the multi-rigid body/finite element mixed analysis is carried out by adopting the deformation body algorithm. The invention solves the problems of low calculation efficiency and low calculation precision of the contact collision problem of the robot mechanical arm. When the contact collision of the robot mechanical arm is analyzed, the rigid body and the deformable body can be converted only by changing the K file, so that the repetitive work is reduced, the technical time is shortened, and the working efficiency is improved.

Description

Multi-rigid body-finite element hybrid analysis method for contact collision of flexible robot manipulators

technical field

The invention belongs to the contact collision analysis technology, in particular to a multi-rigid body-finite element hybrid analysis method for the contact collision of a flexible robot manipulator.

Background technique

With the development of science and technology, robotic arms have been widely used in various fields, such as: aerospace, deep-sea exploration, industry, agriculture, etc. Contact collision is also a common problem of robotic arms in engineering and life applications.

Contact collision is closely related to human life, and has advantages and disadvantages for human production and life, such as: the frictional impact of feet and the ground when walking, the contact collision during the rendezvous and docking process of space probes, and the braking and collision of cars. When dealing with the contact collision problem, it is more to eliminate the adverse effects of the contact collision, such as reducing the wear of the mechanical structure, improving the service life of the machine, and avoiding the additional loss of energy. A long time ago, related scholars have studied the problem of contact collision, and obtained many related theories, which are widely used in the field of machinery. However, the process of contact and collision is a very complicated process, and there are still many problems that remain unsolved.

In the related research for contact collision analysis, a simple method to describe the dynamic contact problem adopts rigid body algorithm, which does not consider the deformation of the object. Although the calculation time of the rigid body algorithm is shorter, it needs to introduce the restitution coefficient, and the calculation accuracy of the rigid body algorithm is low, and the deformation of the contact area or the stress wave cannot be obtained.

The complex method regards the object as a deformable body, adopts the elastic algorithm, and calculates it with the finite element method or the boundary element method. Although the elastic algorithm has high calculation accuracy and can obtain some data that cannot be obtained in the rigid body algorithm, the calculation amount is very large, and the results are often not obtained due to the excessive calculation amount.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator, which solves the problems of low calculation efficiency and low calculation accuracy of finite element analysis of the contact collision problem of the existing robot manipulator.

The technical solution to achieve the purpose of the present invention is: a multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator, the method steps are as follows:

Step 1. Use equivalent units to simulate the bolts and springs in the finite element model of the flexible robot manipulator. The specific steps are as follows:

Step S1, establishing a three-dimensional CAD model of the flexible robot arm;

Step S2, checking the established 3D CAD model;

Step S3, import the three-dimensional CAD model obtained in the step S1 into the Hypermesh preprocessing environment;

Step S4, the hinge bolts and springs in the three-dimensional CAD model obtained in step S1 are deleted, and the remaining part of the mechanical arm is divided into meshes;

In step S5, a rotating hinge unit is established at the position of the hinge bolt deleted in step S4, and a spring unit is established there;

Step S6, define the unit properties and material parameters of the manipulator part and the spring unit, and assign them to them;

Step S7, add loads and constraints, generate a K file solved by a nonlinear finite element solver, and go to step 2.

Step 2. In the calculation process, the rigid body algorithm is used to perform multi-rigid body/finite element hybrid analysis when the flexible robot arm is not in contact; the deformable body algorithm is used to perform multi-rigid body/finite element hybrid analysis when it is in contact. Among them, the specific steps of the conversion between the rigid algorithm and the deformable body algorithm are as follows:

Step S8, determining the start contact time and the contact separation time by calculation;

Step S9, open the K file generated described in step S7, modify, add a statement for rigid body and deformable body conversion, and generate a new K file;

Step S10, import the new K file generated in step S9 into the nonlinear finite element solver for analysis and data processing.

Compared with the prior art, the present invention has a significant advantage in that the joint bolts and springs in the finite element model are simulated by using equivalent elements, and more detailed local treatment is performed in the contact area. In the calculation process, when the manipulator is not in contact, the rigid body algorithm is used for the manipulator, and the deformable body algorithm is used for multi-rigid-finite element hybrid analysis when it is in contact. When analyzing the contact collision of the robot arm, the conversion of rigid body and deformable body can be realized only by changing the K file, which reduces repetitive work, reduces technical time, and improves work efficiency.

Description of drawings

FIG. 1 is a flowchart of a multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator provided by a preferred embodiment of the present invention.

FIG. 2 is a node and coordinate diagram of a spring unit provided by a preferred implementation of the present invention.

FIG. 3 is a finite element model provided by the flexible robot manipulator provided by the preferred embodiment of the present invention.

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings.

Referring to Figure 1, a multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator, the method steps are as follows:

Step 1. Use equivalent units to simulate the bolts and springs in the finite element model of the flexible robot manipulator. The equivalent units include a rotating hinge unit and a spring unit. The rotating hinge unit simulates the hinge bolts of the finite element model, and the spring unit simulates The spring in the finite element model, the specific method is as follows:

Step S1, establishing a three-dimensional CAD model of the flexible robot arm;

Step S2, checking the established 3D CAD model;

Step S3, import the three-dimensional CAD model obtained in the step S1 into the Hypermesh preprocessing environment;

Step S4, the hinge bolts and springs in the three-dimensional CAD model obtained in step S1 are deleted, and the remaining part of the mechanical arm is divided into meshes;

In step S5, a rotating hinge unit is established at the position of the hinge bolt deleted in step S4, and a spring unit is established there;

Step S6, define the unit properties and material parameters of the manipulator part and the spring unit, and assign them to them;

Step S7, add loads and constraints, generate a K file solved by a nonlinear finite element solver, and go to step 2.

Step 2. In the calculation process, when the flexible robot arm is not in contact, the rigid body algorithm is used to perform multi-rigid body/finite element hybrid analysis; when it is in contact, the deformable body algorithm is used to perform multi-rigid body/finite element hybrid analysis. The specific steps are as follows:

Step S8, determining the start contact time and the contact separation time by calculation;

Step S9, open the K file generated in step S7, modify it, add a statement for the conversion of rigid body and deformable body, and generate a new K file; the keywords in the K file converted between the rigid body and the deformed body are as follows :

*DEFORMABLE_TO_RIGID_AUTOMATIC .

Step S10, import the new K file generated in step S9 into the nonlinear finite element solver for analysis and data processing.

The spring unit is a torsion spring unit, and its parameters are stiffness coefficient k and damping coefficient c.

The material property of the rigid body algorithm is set to rigid body, and the material of the deformable body algorithm is set to deformable body or elastic-plastic body.

The rigid body and the deformable body use the same material parameters, and the rigid body and the elastic-plastic body use the same material parameters.

Example 1

As shown in FIG. 3 , the module of the flexible robot arm includes a fixed plate 1 , a double-link mechanical arm connecting shaft 2 , a first link 3 , a spring 4 , a hinge bolt 5 , a second link 6 , and a sliding plate 7 . The fixed plate 1 is fixed on a certain mechanism, one end of the double-link connecting shaft 2 is fixedly connected with the fixed plate 1 , and the other end is rotatably connected with one end of the first link 3 . The other end of the first connecting rod 3 is rotatably connected to one end of the second connecting rod 6 through the spring 4 and the hinge shaft 5 , and the other end of the second connecting rod 6 is in contact with the sliding plate 7 .

In this embodiment, the equivalent unit is a rotating hinge unit and a spring unit, the rotating hinge unit simulates the hinge bolt of the finite element model, and the spring unit simulates the spring in the finite element model. As shown in Figure 2, the two ends of the spring element have I nodes and J nodes respectively, and the parameters of the spring element also include stiffness coefficient k and damping coefficient c. Locally more detailed processing is performed in the contact area; in the calculation process, the rigid body algorithm is used for the robot arm when the robot arm is not in contact, and the multi-rigid body/finite element hybrid analysis is performed using the deformable body algorithm when the robot arm is in contact.

When the manipulator is not in contact, it refers to two stages of separation before and after contact.

The multi-rigid body-finite element hybrid analysis method for the contact collision of a flexible robot manipulator according to the present invention, the specific steps are as follows:

Step 1. Use equivalent units to simulate the bolts and springs in the finite element model of the flexible robot manipulator. The equivalent units include a rotating hinge unit and a spring unit. The rotating hinge unit simulates the hinge bolts of the finite element model, and the spring unit simulates The spring in the finite element model, the specific method is as follows:

Step S1, establishing a three-dimensional CAD model of the flexible robot arm;

Step S2, checking the established 3D CAD model;

Step S3, import the three-dimensional CAD model obtained in the step S1 into the Hypermesh preprocessing environment;

Step S4, the hinge bolts and springs in the three-dimensional CAD model obtained in step S1 are deleted, and the remaining part of the mechanical arm is divided into meshes;

In step S5, a rotating hinge unit is established at the position of the hinge bolt deleted in step S4, and a spring unit is established there;

Step S6, define the unit properties and material parameters of the manipulator part and the spring unit, and assign them to them;

Step S7, add loads and constraints, generate a K file solved by a nonlinear finite element solver, and go to step 2.

Step 2. In the calculation process, when the flexible robot arm is not in contact, the rigid body algorithm is used to perform multi-rigid body/finite element hybrid analysis; when it is in contact, the deformable body algorithm is used to perform multi-rigid body/finite element hybrid analysis. The specific steps are as follows:

Step S8, determining the start contact time and the contact separation time by calculation;

Step S9, open the K file generated in step S7, modify it, add a statement for the conversion of rigid body and deformable body, and generate a new K file; the keywords in the K file converted between the rigid body and the deformed body are as follows :

*DEFORMABLE_TO_RIGID_AUTOMATIC .

Step S10, import the new K file generated in step S9 into the nonlinear finite element solver for analysis and data processing.

In the Hypermesh unit library, the spring unit has axial and torsional properties. Using the torsional properties of the spring unit, the spring unit is named spring in Hypermesh. The parameters that need to be determined when using are: stiffness coefficient k and damping coefficient c are determined by the actual spring parameters are determined.

In Hypermesh, the hinge bolts are deleted, and a rotating hinge unit and a spring unit are established at the hinge.

In order to analyze the contact collision of the flexible robot manipulator, considering that the motion time of the manipulator before the contact is relatively large compared to the time of the contact process, and considering the saving of calculation time, the motion of the manipulator before the contact can be calculated by the multi-rigid body algorithm; collision; The elastic vibration caused by the material will gradually disappear due to the damping of the material, and the motion of the object is mainly rigid motion. In this case, the multi-rigid body algorithm should be used for calculation. However, during the contact process of the object, the contact force has a high frequency and a large amplitude, and the deformation of the object must be considered. Finite element calculation should be used. Therefore, by modifying the K file of LS-DYNA, it is possible to use the deformable body algorithm to calculate only the contact collision process, and use the multi-rigid body algorithm to calculate other motion processes.

Claims (8)

1. a multi-rigid-finite element hybrid analysis method of a flexible robot manipulator contact collision, is characterized in that, the method steps are as follows: Step 1. Use equivalent units to simulate the bolts and springs in the finite element model of the flexible robot arm, and go to step 2; Step 2. In the calculation process, the rigid body algorithm is used to perform multi-rigid body/finite element hybrid analysis when the flexible robot arm is not in contact; the deformable body algorithm is used to perform multi-rigid body/finite element hybrid analysis when it is in contact. 2. The multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator according to claim 1, wherein in the step 1, the equivalent unit comprises a rotating hinge unit and a spring unit, and the rotating hinge The element simulates the hinged bolt in the finite element model, and the spring element simulates the spring in the finite element model. 3. The multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator according to claim 1 or 2, wherein in the above step 1, an equivalent unit is used to simulate the finite element model of the flexible robot manipulator. the bolts and springs, the specific steps are as follows: Step S1, establishing a three-dimensional CAD model of the flexible robot arm; Step S2, checking the established 3D CAD model; Step S3, import the three-dimensional CAD model obtained in the step S1 into the Hypermesh preprocessing environment; Step S4, the hinge bolts and springs in the three-dimensional CAD model obtained in step S1 are deleted, and the remaining part of the mechanical arm is divided into meshes; In step S5, a rotating hinge unit is established at the position of the hinge bolt deleted in step S4, and a spring unit is established there; Step S6, define the unit properties and material parameters of the manipulator part and the spring unit, and assign them to them; Step S7, add loads and constraints, generate a K file solved by a nonlinear finite element solver, and go to step 2. 4 . The multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator according to claim 3 , wherein the spring unit is a torsion spring unit, and its parameters are stiffness coefficient k and damping coefficient c. 5 . 5. The multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator according to claim 3, characterized in that: in the above step 2, the concrete steps of rigid algorithm and deformable body algorithm conversion are as follows: Step S8, determining the start contact time and the contact separation time by calculation; Step S9, open the K file generated described in step S7, modify, add a statement for rigid body and deformable body conversion, and generate a new K file; Step S10, import the new K file generated in step S9 into the nonlinear finite element solver for analysis and data processing. 6 . The multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator according to claim 5 , wherein the conversion between the rigid body and the deformable body is added to generate a statement for the conversion of the rigid body and the deformable body. 7 . The keywords in the new K-file are as follows: *DEFORMABLE_TO_RIGID_AUTOMATIC . 7. The multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator according to claim 5, wherein the material property of the rigid body algorithm is set to rigid body, and the material of the deformable body algorithm is set to deformed body or Elastomeric body. 8 . The multi-rigid body-finite element hybrid analysis method for contact collision of a flexible robot manipulator according to claim 7 , wherein the rigid body and the deformable body adopt the same material parameters, and the rigid body and the elastic-plastic body adopt the same material. 9 . parameter.

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