Browsing by Author "Thornton, Chris"
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- ItemOpen AccessCreating and Evaluating Goal Ordering Structures for Testing Harbour Patrol and Interception Policies(2010-03-24T15:29:21Z) Thornton, Chris; Flanagan, Tom; Denzinger, JoergIn this article, we discuss a method for testing policies that guide groups of agents in simulations for interactions with other agents and the environment that reveal weaknesses of these policies. Our method is based on learning interaction sequences using particle swarm systems and has as one crucial component so-called goal ordering structures that are used to guide the learning towards weakness-revealing interactions. Our discussion centers around the different ways a new measuring idea can be integrated into such an ordering structure using the example of testing patrol and interception policies for harbours. Our experimental evaluation reveals that the position of placement of a new measure in an existing ordering structure can greatly influence the testing results, positively and negatively, but mostly mirrors the intuition associated with the placement.
- ItemOpen AccessVision-Based Stabilization for Fixed-Wing Flight(2011-12-05T17:13:55Z) Boyd, Jeffrey; Thornton, ChrisVision and flight are closely linked, leading to a longstanding interest in how the two are connected. Past research has proposed models for vision in control for biological examples of flight, and there has been recent interest in the use of vision for low-level control of small robotic aircraft such as quad-rotor helicopters. In the work presented here, we show a system for stabilization of a small, fixedwing aircraft in the yaw axis using estimates of parametric optical flow obtained by registration of consecutive video images from a camera mounted on the aircraft. Estimates of angular velocity from the registration replace the values that would otherwise come from a gyro in a conventional stabilization system. No markers or special targets are required – just an environment with enough visual variation to enable image registration. We demonstrate the system in flight and show qualitatively the efficacy of the stabilization from external observation of the aircraft, and from the video acquired from the onboard camera. 1 Introduction