STRUCTURE SYNTHESIS BASED ON FAULT TOLERANT PERFORMANCE FOR REDUNDANT ROBOTS

ZHAO Jing  WEI Shanshan

(College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing 100022)

Abstract: Two fault tolerant performance indexes, reduced condition number and influence factor of fault tolerant workspace are introduced. The former indicates the manipulability of a reduced robot at the moment of a failure. The latter indicates the relative workspace of the reduced robot at this moment. These indexes can quantitatively evaluate the fault tolerant ability of a robot at the moment of a failure and after the failure respectively. Then based on these indexes an optimization method of structural parameters is proposed, which can deter-mine the link length with optimal fault tolerance for a robot. Finally, simulation examples are demonstrated and the sensitivity of fault tolerance of a robot to each link is analyzed with a planar 3R and a spatial 4R robot respectively. The results show that the fault tolerant ability of a robot is more sensitive to the link that is not directly connected with any failed joint or is connected with only one failed joint, which means that these links should be considered in the first place when adjusting link length. In addition, for spatial robots the corresponding relation between the two indexes is not as regular as planar robots, and the conflict between them is not obvious. This implies that it is more possible for spatial robots to simultaneously optimize these two indexes.

Key words: Redundant robots  Fault tolerant performance  Structure synthesis

CLC No: TP242

北京市自然科学基金资助项目(3042005). Received 20061010, received in revised form 20070722