a b s t r a c tThis paper proposes an original set-membership approach for loop detection of mobile robots in the situation where proprioceptive sensors only are available. To detect loops, the new concepts of the t-plane (which is a two dimensional space with time coordinates) are introduced. Intervals of functions (or tubes) are then used to represent uncertain trajectories and tests are provided in order to eliminate parts of the t-plane that do not correspond to any loop. An experiment with an actual underwater robot is proposed in order to illustrate the principle and the efficiency of the approach.

In this paper, a possible solution to track a mobile underwater source in a closed environment with N Autonomous Underwater Vehicles (AUV) in a swarm formation is adressed. The source tracking algorithm is defined as successful when the range between the source and the swarm is sufficiently low during a given duration, short enough to perform a specified action (for example a source localization). A source is defined as an entity that releases a scalar information affected by transport and diffusion in the environment. We use a generic time-varying information f (pi(t)), where pi at time t is the m-dimensional position of a tracker i and function f (.) is a function that represents sensor information. In this paper, we propose an innovative tracking method inspired by the Particle Swarm Optimization (PSO) algorithm that we call the Local Charged Particle Swarm Optimization (LCPSO). The proposed algorithm is adapted to range-dependant communication that characterizes the underwater context and includes flocking parameters. Comparison of the LCPSO against state of the art methods demonstrate the interest of our approach in an underwater scenario.

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Due to the relative low propagation speed of acoustic waves in underwater medium, Underwater Acoustic (UWA) communication is severely impacted by Doppler shift effect especially as the transmission link is related to a system in motion like an Autonomous Underwater Vehicle (AUV). Usually, motioninduced Doppler-shift needs to be estimated and compensated at the UWA receiver side in order to retrieve data. This estimation also provides an information on transmitter/receiver relative speed that is valuable for an underwater mobile like an AUV to perform underwater localization and navigation. In this paper, we consider a reference anchor transmitting UWA data to an AUV in operation. The latter uses UWA communication decoding process to estimate both range and relative speed with respect to the reference point in order to improve its navigation via a conventional Kalman filtering. Simulation results on a shallow water channel demonstrate the Doppler shift estimation to provide substantial enhancement of the underwater localization with respect to a range-only approach.