Research On The Influence Of Limb Of A Family Of 3-dofs Translational Parallel Mechanism On The Performance Of The Mechanism

Parallel mechanism has the advantages of high rigidity,high precision,high bearing capacity,and low-DOF parallel mechanism as an important branch of parallel mechanism,with the characteristic of simple configuration design and control and so on,widely gets the more and more attention.Workspace and singularity are the important indicators to measure performance of parallel mechanism.This article will consider a family of 3-dofs translational parallel mechanism which is by the combination of RRRRR and RPRRR limbs as the research object,and put forward a choosing optimum method for choosing optimum configuration design of this family of parallel mechanism,and work out the optimal workspace and singularity performance mechanism.First of all,based on screw theory analyzing the correlation of constraints screw system of 3-RRRRR,3-RPRRR configuration mechanism,and carrying out the limb structure of these two kinds of configuration mechanism of different degrees of freedom,and then summarizing the configuration in different degrees of freedom of a class of parallel mechanism which by the combination of these two RRRRR,RPRRR limbs,and determining the study object which is a family of 3-dofs translational parallel mechanisms.Then,to study limb characteristics,kinematics analysis is carried out on the two symmetrical parallel mechanisms,and gets the kinematics equation.Using spherical coordinates boundary search method to calculate the workspace,and simulating by using the MATLAB software,then the three-dimensional boundary view is given.Taking workspace volume as the performance index,the influence of the limb structure parameters on the workspace performance is studied.And then,appling of the singularity classification method which was proposed by professor Fang and Tsai to analysis the singularity of the symmetric 3-RRRRR and 3-RPRRR parallel mechanisms,and put forward a singularity discriminant method for this family of parallel mechanisms.According to this method,taking the singularity distribution rate as the singularity performance index,and the influence rule of the limb structure parameters on the singularity performance of the mechanism is studied quantitatively.Finally,by analyzing the influence on the performance from different limb combination,to study the direct mapping from structure class to the mechanism performance with the structure of the class as the input variables,and mechanism performance as the output variables.Based on the mapping relation,the optimal limb combination form is determined,and according to the influence rule of RRRRR and RPRRR limb structure parameters on the workspace and singularity performance,the optimal limb structure is determined,finally accomplishing the limb structure choosing optimum design of this family of parallel mechanism.