This paper describes a method to detect localization failure for mobile robots. In spite of advances in localization methods, mobile robots still may fail in estimating its pose due to degeneration of observations, or unexpected objects around them obstructing observations. We propose a method for mobile robots to monitor these kinds of failures and then take actions for restoring correct localization status.

The software reusability-based development process and reusable objects modeling are discussed. The supporting tools environment which allows both the developer and user to carry out requirement definitions, specification, and implementation in a reusable way, is described. Some quantitative evaluations are given about how productivity and quality have been improved by using this environment, based on the results of a number of case studies made at development sites. Reusability has been largely improved by a software specification adjustment method, called differential specification, and the direct transformation capability offered in the environment.>

An analysis of the effect of multiple narrow-band interfering signals on the probability of error in a frequency-hopped differential phase shift keyed (FH-DPSK) spread-spectrum communication system with a nonlinear receiver is given. In this analysis it is assumed that the sum of the outputs from ann-subchannel receiver is a Gaussian random variable. Subject to this assumption, numerical evaluations of the probability of error for both nonfading and Rayleigh fading channels are presented and compared with those of a linear receiver. The results indicate that the performance of a nonlinear receiver is better than that of a linear receiver for any signal-to-interference ratio.