Chaturvedi, R., Dymond, P. and Jenkin, M. Efficient leader election among numbered agents. Proc. Int. Conf. on Data Engineering and Internet Technology (DEIT) 2011, Bali.
When large groups of agents are tasked to a particular problem it can be useful to be able to elect a leader from among the agents. This leader can then be used to coordinate the agnets to complete the task. But how can we elect a leader for a distributed collection of agnets in an efficient manner? Here we present an algorithm for leader election for a collection of numbered (but unbounded) set of agents. We demonstrate a distributed probabilistic algorithm that the agents can use to elect a leader and to decide that the election is complete.Simulations demonstrate the efficacy of the approach.
Jenkin, M. R., Dyde, R. T., Jenkin, H. L., Zacher, J. and Harris, L. R. Perceptual upright: the relative effectiveness of dynamic and static images under different gravity states. Seeing and Perceiving, 24: 53-64, 2011.
The perceived direction of up depends on both gravity and visual cues to orientation. Static visual cues to orientation have been shown to be less effective in influencing the perception of upright (PU) under microgravity conditions than they are on earth (Dyde et al., 2009). Here we introduce dynamic orientation cues into the visual background to ascertain wheterh they might increase the effectiveness of visual cues in defining the PU under different gravity conditions. Brief periods of microgravity and hypergravity were created using parabolic flight. Observers viewed a polarized, natural scene presented at various orinetations on a laptop viewed through a hood which occluded all other visual cues. The visual background was either an animated video clip in which actors moved along the visual ground plane or an individual static frame from the same clip. We measured the perceptual upright using the orientated character recognition test (OCHART). Dynamic visual cues significantly enhance the effectiveness of vision in determining the perceptual upright under normal gravity conditions. Strong trends were found for dynamic visual cues to produce an increase int he visual effect under both microgravity and hypergravity conditions.
Wang, H., Jenkin, M. and Dymond, P. The relative power of immovable markers in topological mapping. Proc. IEEE International Conference on Robotics and Autonomous Systems (ICRA). Shanghai, China, 2011.
The fundamental problem in robotic exploration and ampping of an unknown environment is answering the question `have I been here before?', which involves disambiguating the robot's current location from previously visited or known locations. One approach to answering this problem in embedded topological worlds is to resort to the use of an external aid that can help the robot disambiguate places. Here we investigate the power of different marker-based aides in exploring undirected topological graphs. We demonstrate the for undirected graphs, certain marker aids are insufficient, whil others have powers taht are sufficient to develop asymptotically optimal exploration algorithms.
Verzijlenberg, B. and Jenkin, M. 6DOF pose estimation using 3D sensors. Proc. IEEE International Conference on Robotics and Autonomous Systems (ICRA). Shanghai, China, 2011.
Pose estimation is an important capability for mobile agents. A wide variety of solutions have been proposed, but work in the literature has focused primarily on solutions for robots whose mobility is restricted to the ground plane. In this work we present a framework for 6DOF pose estimation. Normally the increased computational cost associated with this higher dimensional space makes pose estimation intractable. The approach presented here addresses the computational issues associated with the higher dimensinoal problem by decoupling orientation estimatino from pose estimation. Assuming that orientation can be estimated separately from position allows efficient methods to be used for the (unimodal) orientation estimate, while more sophisticated methods are used for the position estimate. Although similar to Rao-Blackwellization, the approach is essentially reversed. Results on real and simulated datasets and a comparison with a naive 6DOF filter are presented.
Yang, J., Dymond, P. and Jenkin, M. Practicality-based probablisitic roadmaps method. Proc. Canadian Conference on Computer and Robot Vision (CRV). St. John's, NFLD, 2011.
Probabilistic roadmap methods (PRMs) are a commonly used approach to path planning problems in a high-dimensional search space. Although PRMs can often find a solution to solving the path finding problem the solutions are often not practical in that they can cause the device to flail around or to pass very close to obstacles in the environment. This paper presents a variant of PRMs that addresses the practicality problem of the paths found by the planner. A simple and general sample adjustment method is developed, which adjusts the randomly generated nodes that make up the PRM within their local neighborhood to satisfy soft constraints required by the problem. The resulting roadmap can then be used to generate more practical paths. The approach is general and can be adapted to path planning problems with different practical requirements.
Speers, A., Topol, A., Zacher, J., Codd-Downey, R., Verzijlenberg, B. and Jenkin, M. Monitoring underwater sensors with an amphibious robot. Proc. Canadian Conference on Computer and Robot Vision (CRV). St. John's, NFLD, 2011.
The underwater domain provides a wide range of potential applications for autonomous systems. Sessile (immobile) sensor platforms can provide a sensing network to monitor a range of different underwater events. Monitoring such networks can be a challenge, however, as the sensor nodes cn be difficult to monitor and the nature of the medium limits wireless communication. Here we describe an approach that uses an autonomous underwater vehicle to monitor the state of sessile sensors. A visual communication channel is established from the sensor node to the robot that can then communicate the state of the sensor to an underwater- or surface-based operator. This paper describes the basic approach and results of preliminary experiments conducted in robot monitoring of underwater sensors.
Harris, L. R., Jenkin, M., Jenkin, H., Zacher, J. E. and Dyde, R. T. Sensory weighting in space: The Bodies in the Space Environment (BISE) experiment. J. Vest. Res. 21: 72. Presented at the Eighth Symposium on the role of the vestibular organs in space exploration, Houston, TX.
On Earth the perceived direction of "up" can be predicted from a weighted sum of visual, gravity and body orientation cues. The relative weightings of these cues vary from person to person and depend on the task, for example when aligning a line with gravity or when identifying the optimal orientation for object recogniotion. How are the weightings affected when one cue become uninformative? During short periods of microgravity (during parabolic flight) the relative weighting of vision decreased (Dyde et al., 2009, Exp. Brain Res., 196: 647). What is the effect of longer term exposure to microgravity? We meausred perceived orientation changes of seven astronauts before, during and after long-duration space flight. Pre- and post-flight we used the orientated character recognition test (OCHART, Dyde et al., 2006, Exp. Brain Res., 173: 612), shape-from shading and luminous line probes in upright and right-side-down body orientations. On station, subjects performed OCHART early and late in flight. A parallel study used ground-based controls tested at similar intervals. A trend for a reduction in visual influence was observed in flight with lower-than-baseline levels maintained throught six months in orbit. Visual influence was still lower than basedline levels several months after returning to Earth. We conclude that sensory weightings are altered by long-term exposure to microgravity and do not recover within six months returing to Earth. We conclude that sensory weightings are altered by long-term exposure to microgravity and do not recover within six months of returing to normal gravity. These findings will be discussed in terms of sensory adaptation and in comparison to the ground-based control ata.
Harris, L. R., Jenkin, M., Dyde, R. T. and Jenkin, H. Enhancing visual cues to orientation: suggestions for space travellers and the elderly Progress in Brain Research 191: 133-142, 2011.
Establishing our orientation in the world is necessary for almost all aspects of percetion and behavior. Gravity usually defines the critical reference direction. The dreiction of gravity is sensed by somatiosensory detectors indicating pressure points and specialized organs in the vestibular system and viscera that indicate gravity's physical pull. However, gravity's direction can also be snesed visually since we see the effects of gravity on static and moving objects and also deduce its direction from the global structure of a scene indicated by features such as the sky and ground. When cues from either visual or physical sources are comprisomised or ambiguous, perceptual disorientation may result, often with a tendancy to replace gravity with the body's long axis as a reference. Orientation cues are compromised while floating in the weightlessness of space (which neutralizes vestibular and somatosensory cues) or while suspended in netural buoyancy in the ocean (which neutralizes somatosensory cues) and the ability to sense orientation cues may also be compromised in the elderly or in clinical populations. In these situations, enhancing the visual cues to orientation may be beneficial. In this chapter we review research using specially constructed virtual and real environments to quantify the contribution of various visual orientation cues. We demonstrate how visual cues can counteract disorientation by providing effective orientaiton information.
