The use of fault trees for the design of robots for hazardous environments

This paper addresses the application of fault trees to the analysis of robot manipulator reliability and fault tolerance. Although a common and useful tool in other applications, fault trees have only recently been applied to robots. In addition, most of the fault tree analyses in robotics have focused on qualitative, rather than quantitative, analysis. Robotic manipulators present some special problems, due to the complex and strongly coupled nature of their subsystems, and also their wild response to subsystem failures. Additionally, there is a lack of reliability data for robots and their subsystems. There has traditionally been little emphasis on fault tolerance in the design of industrial robots, and data regarding operational robot failures is relatively scarce. However, at this time there is a new and critical need for safe and reliable robots for remote environmental restoration and waste management applications. The question of how to best incorporate fault tolerance and reliability into the design of such remote manipulators remains an open issue, and is the subject of current research. This paper discusses aspects of the reliability problem in robotics, concentrating on the quantitative aspects of fault tree analysis for the design of robot manipulators.