WO2013149429A1

WO2013149429A1 - Design optimization method for serial robot structure

Info

Publication number: WO2013149429A1
Application number: PCT/CN2012/076205
Authority: WO
Inventors: 王太勇; 王润; 刘振忠; 丁彦玉; 邵明堃
Original assignee: 天津大学
Priority date: 2012-04-05
Filing date: 2012-05-29
Publication date: 2013-10-10
Also published as: CN102637228A

Abstract

Disclosed is a design optimization method for a serial robot structure, including: dividing the structure of a robot into multiple modules according to the number of degrees of freedom and a transmission structure; initially designing each of the modules, i.e. primarily determining the shape, thickness and transmission mode of the module; carrying out finite element analysis for the initially designed robot structure, and optimizing the structure through the requirements of the strength, rigidity and natural frequency of the robot; judging whether each module of the robot structure satisfies the requirement of rigidity, if satisfied, continuing, otherwise redesigning same; after performing complete machine simplification for the robot, carrying out modal analysis; and analyzing the formation and frequency, if there is a place not satisfying the requirements of frequency and formation, redesigning same, and if satisfied, completing the design. The present invention adopts finite element and modal analysis for a robot structure to substitute for the conventional empirical method and simple strength checking method, so as to greatly improve the analysis accuracy. By the finite element and modal analysis for the robot structure, the requirements of strength and rigidity of the robot can be met with the minimum consumption of raw materials and cost.

Description

Serial robot structure design optimization method

The invention relates to a structural design of a robot. In particular, it relates to a structural optimization design method for tandem robots using finite element and modal analysis robot structures. Background technique

In recent years, due to rising labor costs, many companies are seeking to use industrial robots instead of labor. At the same time, many industries and high-risk industries that humans cannot do work require robots instead of labor. The structure of the robot not only affects the kinematics and dynamics of the robot, but also affects the control characteristics of the robot. Therefore, the structural design and optimization of the robot is particularly important. The goal of structural optimization is nothing more than The lowest cost meets the design requirements. Since the working environment of industrial robots is relatively harsh and complicated, the effects of vibration and noise cannot be ignored. Therefore, the structure of the tandem robot must not only meet the requirements of its own strength, but also its resonance and fatigue. By knowing the natural frequency and formation of the robot, you can avoid unnecessary losses caused by resonance factors in the robot's work.

The current robot structure optimization mainly has the following problems:

1. Using traditional material mechanics analysis methods, by simplifying the model and relying on empirical formulas to optimize the model, although this method has proved to have certain reliability, sometimes it ignores many important conditions in reality and cannot fully reflect the stress state. .

2. With the optimization algorithm, the objective function is established, the constraint condition is set, and the optimal solution set is generated by the calculation of the algorithm. This method is mostly a theoretically optimal solution, which is often difficult to achieve in reality.

3. When using finite element software, the dependence on network partitioning is high. The accuracy of optimization depends on the sparseness of the grid and the degree of mesh distribution. Summary of the invention

The technical problem to be solved by the present invention is to provide an efficient and feasible serial structure design optimization method combining finite element analysis and modal analysis.

The technical solution adopted by the present invention is: A serial robot structure design optimization method, comprising the following steps: (1) dividing the structure of the robot into a plurality of modules according to the degree of freedom and the transmission structure;

(2) Initial design of each module, that is, preliminary determination of the shape, thickness and transmission mode of the module;

(3) Perform finite element analysis on the robot structure designed for the first step (2), through the strength of the robot, just Degree and natural frequency requirements to optimize the structure;

(4) For the analysis result in step (3), determine whether the respective modules of the robot structure satisfy the requirement of rigidity, if the direct entry step (6) is satisfied, if not, proceed to step (5) for redesign;

(5) In the redesign, if there is a place where only partial modification is needed, the design is returned to step (3) and then analyzed again using the finite element software simulation; if there is a need for the overall modification, return to step (2);

(6) After the machine is simplified, the modal analysis is performed;

(7) Analyze the array and frequency. If there is a requirement that does not meet the frequency and formation requirements, return to step (5) for redesign. If it is satisfied, the design is completed.

The plurality of modules in the step (1) include: a base, a base, a turntable, a swing arm, an arm and a joint top.

The finite element analysis described in step (3) includes the following three steps:

a) Using the trajectory optimization to find the trajectory of the robot from the start point to the end point, that is, the angular velocity change value of each joint during the movement of the robot, and save the obtained value in txt format for storage;

b) Introduce the angular velocity change value obtained in step a) into the simulation software motion, and set the constraints, contact and gravity in the simulation software motion to simulate the realistic environment, thereby generating the force of each component during the working process;

c) Analyze the finite element software si dish lation, set the constraint, add force and mesh, run the result, and observe the stress value of the analysis result to obtain the stiffness intensity distribution of the component.

After the simplification of the whole machine is performed in step (6), the modal analysis is performed. The frequency example is generated in the finite element software simulation, and the natural frequency and formation of the robot are obtained, and the robot structure is obtained from the formation and the natural frequency. Requires the need for improvement and redesign.

The serial robot structural design optimization method of the invention replaces the traditional empirical method and the simple strength checking method by using the finite element and modal analysis robot structure, thereby greatly improving the analysis accuracy. The invention first optimizes the various components of the robot to achieve the strength requirement at a minimum cost, and then performs modal analysis on the whole machine, and the rigidity of each transmission joint of the robot can be seen through the formation. This not only achieves the strength of the various components of the robot structure, but also meets the stiffness requirements of the transmission joints, so that the robot structure is optimized. The invention achieves the strength and rigidity requirements of the robot by finite element and modal analysis of the robot structure, minimum consumption of raw materials and costs. DRAWINGS

1 is a schematic diagram and a flow chart for optimizing a structural design of a serial robot according to the present invention;

Figure 2 is an effect diagram of analyzing the stress results by the method of the present invention; 3 is an effect diagram of analyzing a robot's first six-order modal array obtained by the method of the present invention, wherein (a), (b), (c), (d), (e), (f) respectively correspond to the robot front 6th-order formation. detailed description

The serial robot structure design optimization method of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

As shown in FIG. 1, the method for optimizing the structural design of the serial robot of the present invention comprises the following steps:

(1) The structure of the robot is divided into multiple modules according to the degree of freedom and the transmission structure, including six modules: base, base, turntable, swing arm, arm and joint top;

(3) Perform a finite element analysis on the robot structure of the first design in step (2), and optimize the structure by the requirements of the strength, rigidity and natural frequency of the robot; the finite element analysis described above includes the following three steps:

b) Introduce the angular velocity change value obtained in step a) into the simulation software motion, and set the constraints, contact and gravity in the simulation software motion to simulate the real environment, so as to generate the force of each component during the working process;

c) Analyze using the finite element software si lation, set constraints, add force and mesh, run the results, and observe the stress values of the analysis results to obtain the stiffness distribution of the components.

(4) For the analysis result in the step (3), determine whether the respective modules of the robot structure satisfy the requirement of rigidity, if the direct entry step (6) is satisfied, if not, proceed to step (5) for redesign;

(5) In the redesign, if there is a place where only partial modification is needed, the design is returned and the step (3) is returned again using the finite element software simulation; if there is a need for the overall modification, return to step (2);

(6) After the machine is simplified, the modal analysis is performed;

After the simplification of the whole machine is performed, the modal analysis is performed. The frequency example is generated in the finite element software simulation, and the natural frequency and formation of the robot are obtained. From the formation and the natural frequency, the robot structure needs to be improved. Part of the redesign.

The method for optimizing the structural design of the tandem robot of the present invention will be specifically described below.

According to the structure of the serial robot and the characteristics of the transmission, the robot structure is divided into six modules: base, base, turntable, swing arm, arm and joint top. Perform the initial design of the module structure, initially determine the shape, thickness and transmission of each module Way of moving.

In the motion simulation software, after selecting the motion example, add six motors of the six-degree-of-freedom series robot, set the rotation direction, and use the interpolation method to import the angular velocity values planned by matlab using the interpolation method to set the gravitational value of the whole environment. And direction to simulate the gravity field in the real environment, adding contact constraints to avoid the collision of robot parts during the movement. After simulating the motion process from the start point to the end point, the force of each component can be listed as a chart. Table 1 below shows the force of the main components of the robot measured by simulation.

Table 1 List of main components stress

In the finite element simulation, the finite element analysis is performed on the six main components. Taking the turntable as an example, the constraints and the direction of the added force are defined according to the actual situation. Draw a grid to add mesh constraints in local areas. Figure 2 is an effect diagram of the analysis of the stress results. From the figure, it can be seen that the stress at the upper edge of the ear is the maximum (605800. 4N/M~2). Exceeding the material strength, it can be increased by thickening and reinforcement. Strength, while reducing the thickness at a safer place to save material. The other components are optimized in the same way.

Simplified tandem robot modeling has been imported into the simulation, creating frequency studies, setting the joints between the various components, and adding fixed constraints on the robot base to the ground. Dividing the mesh, because the natural frequency and mode shape mainly depend on the structural mass and stiffness distribution, there is no similar stress concentration phenomenon, and the uniform mesh can make the structural stiffness matrix and the elements of the mass matrix not too different. Therefore, in the modal analysis, it is not necessary to use the grid control, and the grid can be divided normally. The grid value is set as shown in Table 2 below.

Table 2 Grid parameters

Since the actual analysis object is infinite dimensional, its mode has infinite order, but only the first few modes are dominant for the motion, so the first few modes are calculated according to the needs. The results of the frequency analysis are shown in Table 3 below, and the arrays of the first 6 stages of the robot correspond to the a to f diagrams in Fig. 3, respectively. Table 3 The first 6 natural frequencies of the robot

(1) Due to the mass of the extension of the robot in the mode of the tandem robot, the lower the lower frequency of the overall mechanism. It can be seen from the table that the first-order mode of the mechanism is not low, and it satisfies the international requirement that the first-order natural frequency of the 12kg robot is not less than 12Hz, indicating that the quality of the mechanism is not large.

(2) It can be seen from the 2nd, 3rd, 4th, and 5th order forms shown by b, c, d, and e in Fig. 3 that the distortion occurs at the joint between the turntable and the arm. The deformation of the bending and bending and twisting, therefore, it can be judged that the rigidity of the transmission mechanism of the mechanism at the turntable and the arm is insufficient, and the transmission mode and structure here need to be redesigned.

(3) It can be seen from the 5th and 6th-order formations shown by e and f in Fig. 3 that the distortion between the base and the swing arm indicates that the rigidity of the joint is insufficient, and it is necessary to add a rib to the part and increase the thickness. .

Through the modification of the above finite element analysis and modal analysis, the modification is carried out, and then the analysis is carried out again, thereby achieving the closed loop of the entire design to the optimization process, and ensuring that the robot optimized by the design of the method can meet the expected Claim.

Claims

Rights request

A method for optimizing a structural design of a tandem robot, comprising the steps of:

(1) Divide the structure of the robot into multiple modules according to the degree of freedom and the transmission structure;

(3) Perform a finite element analysis on the robot structure of the first design in step (2), and optimize the structure by the requirements of the strength, rigidity and natural frequency of the robot;

(6) After the machine is simplified, the modal analysis is performed;

The method for optimizing the structure design of the serial robot according to claim 1, wherein the plurality of modules in the step (1) comprises: a base, a base, a turntable, a swing arm, an arm and a joint top. Modules.

3. The method for optimizing the structural design of a tandem robot according to claim 1, wherein the performing the finite element analysis in the step (3) comprises the following three steps:

The method for optimizing the structure design of the serial robot according to claim 1, wherein after the simplification of the whole machine is performed in step (6), the modal analysis is performed, and the frequency calculation is generated in the finite element software simulation. For example, the natural frequency and formation of the robot are obtained, and the parts of the robot structure that need to be improved are obtained from the formation and the natural frequency, and redesigned.