Overall availability of a robot with internal safety device

We introduce a robot-safety device system composed of a robot with internal (built-in) safety device. The system is characterized by a safety shut-down rule and by the natural feature of standby. In order to obtain the point availability of the twin-system, we introduce a stochastic process endowed with a time-dependent potential satisfying an integro-differential equation. The explicit solution procedure requires the (new) notion of ineffective lifetime - versus - effective lifetime of the robot. The analysis of the long-run availability requires the introduction of a signed measure. As an example, we display a computer-plotted graph of the point availability obtained by inversion of the corresponding Laplace-transform. (C) 2008 Elsevier Ltd. All rights reserved.