首先,根据基于方位特征(POC)和有序单开链(SOC)的并联机构结构降耦原理,设计了一类5种5-SPS直线型动平台并联机构,其中,4种为本文提出的新机构;同时,提出了机构的存在性判别式,并据此证明了5种5-SPS直线型动平台机构的存在性,以及6-SPS、4-SPS、3-SPS、2-SPS直线动平台机构的非存在性;其次,对5种5-SPS直线型动平台并联机构的耦合度、输出方位特征、输入-输出运动解耦性等3个重要拓扑结构特性,以及位置工作空间特性,分别进行了计算与比较,结果表明:直线动平台上球副重合可降低机构耦合度及其位置正解求解的难度,但同时会使位置工作空间减小;含三重球副的机构具有输入-输出运动部分解耦性。
Parallel mechanisms with linear moving platform( LMP) have good practical application value,but it was rarely studied. Firstly,using structure coupling-reducing theory based on the position and orientation characteristics( POC) and the ordered single-open-chain( SOC) units,five 5-SPS parallel mechanisms with LMP were designed, and four of them were novel ones. Secondly, the"existence criterion of mechanism"was proposed. Each 5-SPS parallel mechanisms with LMP had its own advantages and applications. Accordingly,the existence of five 5-SPS and the non-existence of 6-SPS,4-SPS,3-SPS,2-SPS parallel configurations with LMP were proved. As a consequence,the criterion can be used to determine the existence of mechanisms. Then,the three important topological characteristics,including coupling degree,the output POC and the input-output motion decoupling,as well as the position workspace characteristics,of the five 5-SPS parallel mechanisms with LMP were separately calculated and compared. It was shown that the coupling degree of mechanisms and difficulty of solving forward displacement analysis can be reduced,but the workspace would be reduced simultaneously when the collinearing or coinciding of the spherical joints on the moving platform was occurred. And the mechanisms with triple-spherical-joint structure had input-output motion decoupling. These results can provide theoretical basis for engineering design,optimal selection and potential use of the five 5-SPS parallel mechanisms with LMP.