Cooperative decentralised circumnavigation with application to algal bloom tracking

Abstract

Harmful algal blooms occur frequently and deteriorate water quality. A reliable method is proposed in this paper to track algal blooms using a set of autonomous surface robots. A satellite image indicates the existence and initial location of the algal bloom for the deployment of the robot system. The algal bloom area is approximated by a circle with time varying location and size. This circle is estimated and circumnavigated by the robots which are able to locally sense its boundary. A multi-agent control algorithm is proposed for the continuous monitoring of the dynamic evolution of the algal bloom. Such algorithm comprises of a decentralised least squares estimation of the target and a controller for circumnavigation. We prove the convergence of the robots to the circle and in equally spaced positions around it. Simulation results with data provided by the SINMOD ocean model are used to illustrate the theoretical results.

Non-uniform Observability for Moving Horizon Estimation and stability with respect to additive perturbation

“…We show notably that in the sensorcentric point of view, the dynamics of the robot is not important for our concept of observability and only its state and input trajectories matter. Besides, the notion of circumnavigation appears to be useful in SLAM and related problems of localisation of autonomous systems, see [11,17,16,38,40,41]. Inspired by this, we finally show that 2D SLAM systems with different types of sensors can be made simultaneously weakly-regularly observable if the robot tracks any circular trajectory in the position/velocity space.…”

“…The estimation problem for these models has been mostly recently tackled in the literature by using optimization based techniques, see [8,21]. One is usually interested in solving the associated Problem (FIE t,u ) in an offline way for system ( 16)- (17). In this context, the variables are the initial robot state and the positions of the landmark written generically as ζ 0 for the initial state of the robot and m for the set of landmarks.…”

“…As a consequence, the second contribution of this paper is the analysis of sufficient conditions for weak regular persistence of the landmark-based SLAM system ( 16)- (17) in the spirit of Proposition 20 both with a worldcentric and sensor-centric view.…”

Cooperative Circumnavigation for a Mobile Target Using Adaptive Estimation

“…We simulated this proposed system using a man made random data set to represent a circular target. The current paper significantly extends our IROS 2019 publication [13], which focuses on how to circumnavigate an algal bloom shape. In both we wish to track a circular shape but the assumptions, methods and results are different.…”

Robotic Path Following in 3D Using a Guiding Vector Field

“…In circular formation control, multiple robots either need to move to or initially start on a specified circle, and then move along the circle until some desired arc distances are achieved via local communication [17]- [23]. Circumnavigation control additionally requires all robots to keep moving along the circle to fulfill some tasks, such as escorting an important target [24]- [32]. However, these studies are all restricted to 2D circular paths, and many of them impose additional requirements on the robots' initial positions (e.g., to maintain the order preservation [21], [22]).…”