Design of Modular Fault Tolerant Manipulators

Christiaan J.J. Paredis and Pradeep K. Khosla

Abstract: In this paper, we deal with two important issues in relation to modular reconfigurable manipulators, namely, the determination of the modular assembly configuration optimally suited to perform a specific task and the synthesis of fault tolerant systems. We present a numerical approach yielding an assembly configuration that satisfies four kinematic task requirements: reachability, joint limits, obstacle avoidance and measure of isotropy. Further, because critical missions may involve high costs if the mission were to fail due to a failure in the manipulator system, we address the property of fault tolerance in more detail. We prove the existence of fault tolerant manipulators and develop an analysis tool to determine the fault tolerant work space. We also derive design templates for spatial fault tolerant manipulators. For general purpose manipulators two redundant degrees-of-freedom are needed for every order of fault tolerance. However, we show that only one degree of redundancy is sufficient for task specific fault tolerance.

in The Algorithmic Foundations of Robotics, eds. K. Goldberg et al., A. K. Peters, Boston, Ma, 1995.