CN108393928A - Multi-rigid body-finite element hybrid analysis of flexible robot's robot contact collision - Google Patents

Abstract

The invention discloses a kind of multi-rigid body finite element hybrid analysis of flexible robot's robot contact collision, and the link bolt and spring in finite element model are simulated using equivalent unit；In calculating process, mechanical arm not in contact with when rigid body algorithm used using mechanical arm, multi-rigid body/finite element hybrid analysis is carried out using deformable body algorithm when contact.The present invention's solves the problems, such as the low problem low with computational accuracy of robot arm contact-impact computational efficiency.When analyzing robot arm contact-impact, it is only necessary to by changing K files, so that it may to realize the conversion of rigid body and deformable body, reduce repetitive work, reduce the technology time, improve working efficiency.

Description

Multi-rigid body-finite element hybrid analysis method for contact collision of flexible robotic arm

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 the mechanical arm of a flexible robot.

Background technique

With the development of science and technology, robot manipulators 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 daily life applications.

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

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

The complex method regards the object as a deformable body, adopts elastic algorithm, and calculates with finite element method or 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 often the result cannot be obtained due to the excessive calculation amount.

Contents of the invention

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

The technical solution to realize the object of the present invention is: a multi-rigid body-finite element hybrid analysis method of a flexible robotic arm contact collision, the method steps are as follows:

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

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

Step S2, checking the established 3D CAD model;

Step S3, importing the three-dimensional CAD model obtained in the step S1 into the Hypermesh pre-processing environment;

Step S4, deleting the hinged bolts and springs in the three-dimensional CAD model obtained in step S1, and dividing the remaining mechanical arm parts into meshes;

Step S5, establishing a rotary hinge unit at the position of the hinge bolt deleted in step S4, and establishing a spring unit there;

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

Step S7, adding loads and constraints, generating a K file solved by a nonlinear finite element solver, and turning to step 2.

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

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

Step S9, open the K file generated in step S7, modify it, add sentences 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 a nonlinear finite element solver for analysis and data processing.

Compared with the prior art, the present invention has the remarkable advantage that equivalent elements are used to simulate the hinged bolts and springs in the finite element model, and local more detailed 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 body-finite element hybrid analysis when it is in contact. When analyzing the contact collision of the robot manipulator, only by changing the K file, the conversion between the rigid body and the deformable body can be realized, which reduces repetitive work, reduces technical time, and improves work efficiency.

Description of drawings

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

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

Fig. 3 is a finite element model provided by the flexible robotic arm provided by the preferred embodiment of the present invention.

Detailed ways

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

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

Step 1. Use equivalent elements to simulate the bolts and springs in the finite element model of the flexible robot arm, where the equivalent elements include a rotating hinge element and a spring element, the rotating hinge element simulates the hinge bolt of the finite element model, and the spring element 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 robotic arm;

Step S2, checking the established 3D CAD model;

Step S3, importing the three-dimensional CAD model obtained in the step S1 into the Hypermesh pre-processing environment;

Step S4, deleting the hinged bolts and springs in the three-dimensional CAD model obtained in step S1, and dividing the remaining mechanical arm parts into meshes;

Step S5, establishing a rotary hinge unit at the position of the hinge bolt deleted in step S4, and establishing a spring unit there;

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

Step S7, adding loads and constraints, generating a K file solved by a nonlinear finite element solver, and turning to step 2.

Step 2. During 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 contact start time and contact separation time by calculation;

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

*DEFORMABLE_TO_RIGID_AUTOMATIC .

Step S10, import the new K file generated in step S9 into a 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 as a rigid body, and the material property of the deformable body algorithm is set as a deformable body or an 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 Figure 3, the module of the flexible robotic arm includes a fixed plate 1, a double-link mechanical arm connecting shaft 2, a first connecting rod 3, a spring 4, a hinge bolt 5, a second connecting rod 6, and a sliding plate 7 . The fixed disk 1 is fixed on a certain mechanism, one end of the double-link connecting shaft 2 is fixedly connected with the fixed disk 1, and the other end is rotationally connected with one end of the first connecting rod 3 . The other end of the first connecting rod 3 is rotationally connected with 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 rotary hinge unit and a spring unit, the rotary 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 Fig. 2, the two ends of the spring element have node I and node J respectively, and the parameters of the spring element also include stiffness coefficient k and damping coefficient c. Local and more detailed processing is carried out in the contact area; in the calculation process, the mechanical arm adopts the rigid body algorithm when the mechanical arm is not in contact, and the deformable body algorithm is used for multi-rigid body/finite element hybrid analysis when in contact.

When the arms are not in contact, we refer to the two phases of separation, pre-contact and post-contact.

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

Step 1. Use equivalent elements to simulate the bolts and springs in the finite element model of the flexible robot arm, where the equivalent elements include a rotating hinge element and a spring element, the rotating hinge element simulates the hinge bolt of the finite element model, and the spring element 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 robotic arm;

Step S2, checking the established 3D CAD model;

Step S3, importing the three-dimensional CAD model obtained in the step S1 into the Hypermesh pre-processing environment;

Step S4, deleting the hinged bolts and springs in the three-dimensional CAD model obtained in step S1, and dividing the remaining mechanical arm parts into meshes;

Step S5, establishing a rotary hinge unit at the position of the hinge bolt deleted in step S4, and establishing a spring unit there;

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

Step S7, adding loads and constraints, generating a K file solved by a nonlinear finite element solver, and turning to step 2.

Step 2. During 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 contact start time and contact separation time by calculation;

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

*DEFORMABLE_TO_RIGID_AUTOMATIC .

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

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

In Hypermesh, the hinge bolts are deleted, and the rotational hinge unit and spring unit are established at the joint.

In order to analyze the contact collision of the flexible robot manipulator, considering that the movement time before the contact of the manipulator is relatively large compared with the time of the contact process, and considering the saving of calculation time, the motion of the robot manipulator before the contact can be calculated by the multi-rigid body algorithm; the collision The resulting elastic vibration will gradually disappear due to material damping, and the motion of the object is mainly manifested as rigid motion. At this time, 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. It is suitable to use finite element calculation. Therefore, by modifying the K file of LS-DYNA, it is possible to realize the purpose of calculating with deformable body algorithm only in the process of contact and collision, and using multi-rigid body algorithm for other motion processes.

Claims (8)

1. a kind of multi-rigid body-finite element hybrid analysis of flexible robot's robot contact collision, which is characterized in that method Steps are as follows：

Step 1, using equivalent unit simulate flexible robot's mechanical arm finite element model in bolt and spring, be transferred to step 2；

Step 2, in calculating process, flexible robot's mechanical arm not in contact with when using rigid body algorithm carry out multi-rigid body/finite element Hybrid analysis；Multi-rigid body/finite element hybrid analysis is carried out using deformable body algorithm when contact.

2. multi-rigid body-finite element hybrid analysis of flexible robot's robot contact collision according to claim 1, It is characterized in that：In the step 1, equivalent unit includes a rotation hinge unit and a spring unit, rotating hinge order The link bolt of member simulation finite element model, spring unit simulate the spring in finite element model.

3. multi-rigid body-finite element hybrid analysis side of flexible robot's robot contact collision according to claim 1 or 2 Method, which is characterized in that in above-mentioned steps 1, the spiral shell in the finite element model of flexible robot's mechanical arm is simulated using equivalent unit Bolt and spring, are as follows：

Step S1 establishes the three-dimensional CAD model of flexible robot's mechanical arm；

Step S2 checks established three-dimensional CAD model；

The three-dimensional CAD model obtained in the step S1 is imported into Hypermesh pre-treatment environment by step S3；

Step S4, by the three-dimensional CAD model obtained in step S1 link bolt and spring delete, and by remaining mechanical arm Part carries out the division of grid；

Step S5 establishes rotation hinge unit at the position for the link bolt deleted in step s 4, while establishing bullet at this Spring unit；

Step S6, defines the cell attribute and material parameter of mechanical arm section and spring unit, and is given to them；

Step S7 adds load and constraint, generates the K files solved with nonlinear finite element solver, is transferred to step 2.

4. multi-rigid body-finite element hybrid analysis of flexible robot's robot contact collision according to claim 3, It is characterized in that, the spring unit is torsionspring unit, parameter is stiffness coefficient k and damped coefficient c.

5. multi-rigid body-finite element hybrid analysis of flexible robot's robot contact collision according to claim 3, It is characterized in that：In above-mentioned steps 2, Stiff algorithms and the conversion of deformable body algorithm are as follows：

The time for starting time of contact and contact separation is determined by calculation in step S8；

The K files generated described in step S9, opening steps S7, modify, and the sentence converted for rigid body and deformable body is added, Generate new K files；

The new K files generated in step S9 are imported into nonlinear finite element solver and carried out at analysis and data by step S10 Reason.

6. multi-rigid body-finite element hybrid analysis of flexible robot's robot contact collision according to claim 5, It is characterized in that：Keyword in the K files converted between the rigid body and deformable body is as follows：

*DEFORMABLE_TO_RIGID_AUTOMATIC 。

7. multi-rigid body-finite element hybrid analysis of flexible robot's robot contact collision according to claim 5, It is characterized in that：The material properties of the rigid body algorithm are set as rigid body, and the material of deformable body algorithm is set as deformable body or bullet Plastomer.

8. multi-rigid body-finite element hybrid analysis of flexible robot's robot contact collision according to claim 5, It is characterized in that：The rigid body uses same material parameter, rigid body to use same material parameter with lastics with deformable body.