• Bio-inspired coverage of invisible hazardous substances in the environment

      Oyekan, John O.; Hu, Huosheng; Gu, Dongbing; University of Essex (World Scientific Publishing Company, 2010)
      Inspired by the simplicity of how nature solves its problems, a controller based upon the bacteria chemotaxis behavior and flocking of starlings in nature is developed and presented. It would enable the localization and subsequent mapping of pollutants in the environment. The pollutants could range from chemical leaks to invisible air borne hazardous materials. Simulation is used to explore the feasibility of the proposed controller and then a brief discussion on how to implement it onto a real robotic platform is presented. By using the advantages offered by swarm robotics, it is possible to achieve a collective mapping of an invisible pollutant spread over a large area. The approach presented is very simple, computational efficient, easily tuned and yet highly effective (desirable characteristics of biological systems) in generating a representation of an invisible pollutant.
    • Geometric polarimetry—part I: spinors and wave states

      Bebbington, David; Carrea, Laura; University of Essex (IEEE, 2014-07)
      A new formal approach for the representation of polarization states of coherent and partially coherent electromagnetic plane waves is presented. Its basis is a purely geometric construction for the normalized complex-analytic coherent wave as a generating line in the sphere of wave directions and whose Stokes vector is determined by the intersection with the conjugate generating line. The Poincaré sphere is now located in physical space, simply a coordination of the wave sphere, with its axis aligned with the wave vector. Algebraically, the generators representing coherent states are represented by spinors, and this is made consistent with the spinor-tensor representation of electromagnetic theory by means of an explicit reference spinor that we call the phase flag. As a faithful unified geometric representation, the new model provides improved formal tools for resolving many of the geometric difficulties and ambiguities that arise in the traditional formalism.
    • Mobile sensor networks for modelling environmental pollutant distribution

      Lu, Bowen; Oyekan, John O.; Gu, Dongbing; Hu, Huosheng; Nia, Hossein Farid Ghassem; University of Essex (Taylor and Francis, 2011)
      This article proposes to deploy a group of mobile sensor agents to cover a polluted region so that they are able to retrieve the pollutant distribution. The deployed mobile sensor agents are capable of making point observation in the natural environment. There are two approaches to modelling the pollutant distribution proposed in this article. One is a model-based approach where the sensor agents sample environmental pollutant, build up an environmental pollutant model and move towards the region where high density pollutant exists. The modelling technique used is a distributed support vector regression and the motion control technique used is a distributed locational optimising algorithm (centroidal Voronoi tessellation). The other is a model-free approach where the sensor agents sample environmental pollutant and directly move towards the region where high density pollutant exists without building up a model. The motion control technique used is a bacteria chemotaxis behaviour. By combining this behaviour with a flocking behaviour, it is possible to form a spatial distribution matched to the underlying pollutant distribution. Both approaches are simulated and tested with a group of real robots.