Analysis of robots for hazardous environments

Abstract

& CONCLUSIONS Reliability analysis of fault tolerant systems often ignores the small probability that a failure might not be detected or, if detected, may not be properly handled. The probability that the failure is detected and properly handled is called coverage. Inclusion of coverage in reliability analysis is especially important when analyzing critical systems, systems: which for some reason are not easily reparable, or systems whose failure can result in serious damage to the system or its surroundings. One example of a system which can cause such damage is a robot manipulator arm. Robots are being increasingly employed in remote and hazardous environments such as in space and in nuclear waste cleanup, and can exhibit a wild response to subsystem failure, damaging themselves and/or their surroundings. Addition of redundancy to such systems can increase their reliability by allowing continued operation in the presence of faults (provided that the fault is covered), an advantage in a system where repair is difficult or impossible. Coverage models have been used to analyze the behavior of fault-tolerant computer systems in the presence of faults, providing an estimate of the relative probability of an uncovered vs. a covered component failure (given that a fault has occurred) [l]. This paper extends the use of coverage models to the basic components of the joint of a robot and presents data utilizing the calculated coverage for a three-joint robot manipulator arm designed to operate in the plane.

Optimal mapping of joint faults into healthy joint velocity space for fault-tolerant redundant manipulators

“…The manipulators in this paper are assumed to be revolute joint manipulators. Forward kinematics relates joint angles (2) to EFF positional and orientational variables (3).…”

“…1,2 This fact has been noticed for the teleoperated manipulators for handling of hazardous or explosive chemicals. 3,4 Design and control of faulttolerant manipulator aim to maintain the dependability of the manipulator despite of partial failures. The fault might occur in the actuators or the sensors of the manipulator.…”

Reliability maps for probabilistic guarantees of task motion for robotic manipulators

“…E-mail: hamid.abdi@deakin.edu.au and reliability of surgical robots are critical to prevent patient injury because of robot failure [3,4]. This is true for most applications of fault-tolerant robots from 5 space exploration to hazardous material disposal where the robot failure can result in a catastrophic outcome [5][6][7][8][9]. Fault tolerance is important because it increases the dependability of the robots.…”

Evaluating the reliability of prototype degradable systems

“…However, while fault trees are very useful, they are somewhat limited in their applications. Partial failures, coverage, repairable systems, and other important reliability issues are not covered well by the fault tree approach, although recent developments in fault tree analysis are expanding the range of application somewhat [19,20]. Markov modeling is a valuable tool for dealing with the above situations, and indeed, is often used in the special cases mentioned above.…”