Fault tolerance via analytic redundancy for a modularized sensitive skin

As sensor arrays become ever larger in complex automation systems, provisions for sensor fault detection and tolerance become mandatory. This work addresses the question of real-time fault tolerance in large two-dimensional sensor arrays, with the number of sensors on the order of thousands or more. As an example, we consider a flexible sensitive skin system with uniformly distributed infrared sensors. The purpose of the skin is to cover the whole body of a mobile robot or a robot arm manipulator, and serve as a front end of a motion planning and collision avoidance system. The goal of the proposed approach to fault tolerance is to maintain machine's functionality in situations with damaged sensors; without it, erroneous motion or collisions with surrounding objects would occur. The approach makes use of analytic redundancy whereby periodical comparison is made of sensor measurements with dynamically adjusted expected values of sensor readings. Two fault tolerance schemes, online and off-line, are considered. The properties of both schemes are analyzed and results of experiments demonstrating their performance are discussed.