Abstract:

The side effects of error sources on the motion precision of a spherical parallel mechanisms were treated as a kind of mechanical system faults,a new concept named precision fault tolerance and its basic idea were presented herein.Degree of precision fault tolerance(DOPFT) was defined as an index for describing the precision fault tolerance ability of the spherical parallel mechanisms. Based on screw theory and over-constrained analysis, m-RRR(m≥4) spherical parallel mechanisms were designed, which had the same kinematic performance with spherical 3-RRR parallel mechanism.Their precision fault tolerance performances were compared via computation of DOPFTs,simulation researches were also conducted. Simulation results show that the fault tolerance strategy based on DOPFT can enhance the motion precision of spherical parallel mechanism and eliminate side effect of error sources on the motion precision of spherical parallel mechanisms effectively.

Key words: spherical parallel mechanism, precision, fault tolerance, over-constrained, redundancy actuation

摘要：

将误差源对球面并联机构运动精度的不利影响看作一种机械系统故障,提出了球面并联机构精度容错的概念和基本思想,定义了描述球面并联机构精度容错能力的指标——精度容错度。基于螺旋理论,利用球面3-RRR并联机构的过约束性设计了具有冗余驱动的球面m-RRR(m≥4)型改进机构。通过求解原机构和改进机构的精度容错度,比较了它们的精度容错能力,并结合实例进行了仿真研究,结果表明所提出的以精度容错度为依据的精度容错策略能有效提高球面并联机构的精度,克服误差源的不良影响。



关键词: 球面机构, 精度, 容错, 过约束, 冗余驱动