Recognition of Kinematic Joints of 3D Assembly Models Based on Reciprocal Screw Theory

Tao Xiong,Wenjie Hou,Yizhong Wu,Liping Chen,Jianwan Ding

doi:10.1155/2016/1761968

Tao Xiong, Wenjie Hou + Show 3 more

Open Access

https://doi.org/10.1155/2016/1761968

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Abstract

Reciprocal screw theory is used to recognize the kinematic joints of assemblies restricted by arbitrary combinations of geometry constraints. Kinematic analysis is common for reaching a satisfactory design. If a machine is large and the incidence of redesign frequent is high, then it becomes imperative to have fast analysis-redesign-reanalysis cycles. This work addresses this problem by providing recognition technology for converting a 3D assembly model into a kinematic joint model, which is represented by a graph of parts with kinematic joints among them. The three basic components of the geometric constraints are described in terms of wrench, and it is thus easy to model each common assembly constraint. At the same time, several different types of kinematic joints in practice are presented in terms of twist. For the reciprocal product of a twist and wrench, which is equal to zero, the geometry constraints can be converted into the corresponding kinematic joints as a result. To eliminate completely the redundant components of different geometry constraints that act upon the same part, the specific operation of a matrix space is applied. This ability is useful in supporting the kinematic design of properly constrained assemblies in CAD systems.

Highlights

We can design a machine in terms of a top-down approach or a bottom-up approach in a CAD system
We propose a new method to automatically convert a 3D assembly model into a screw system based on reciprocal screw theory
(iii) We eliminate the redundant components of different geometry constraints that act upon the same part by the specific operation of a matrix space

Summary

Introduction

We can design a machine in terms of a top-down approach or a bottom-up approach in a CAD system. According to [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29], if the screw representations between any two parts of the assembly model are known, we can analyze the model’s kinematic functions. A screw system can be used for kinematic analysis, such as determining the degrees of freedom, estimating the reaction of constraints, and characterizing the nature of contacts between any two components.

Screw Models of Kinematic Joints

Reciprocal Screw Models of Geometric Constraints

Recognition of Kinematic Joints

Examples

B11 B4

Conclusions