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Zhang, Fumin

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Now showing 1 - 5 of 5
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    Cooperative Exploration of Level Surfaces of Three Dimensional Scalar Fields
    (Georgia Institute of Technology, 2011) Wu, W. ; Zhang, Fumin
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    Battery Level Estimation of Mobile Agents Under Communication Constraints
    (Georgia Institute of Technology, 2010-06) Kim, Jonghoek ; Zhang, Fumin ; Egerstedt, Magnus B.
    Consider a team of mobile agents monitoring large areas, e.g. in the ocean or the atmosphere, with limited sensing resources. Only the leader transmits information to other agents, and the leader has a role to monitor battery levels of all other agents. Every now and then, the leader commands all other agents to move toward or away from the leader with speeds proportional to their battery levels. The leader then simultaneously estimates the battery levels of all other agents from measurements of the relative distances between the leader and other agents. We propose a nonlinear system model that integrates a particle motion model and a dynamic battery model that has demonstrated high accuracy in battery capacity prediction. The extended Kalman filter (EKF) is applied to this nonlinear model to estimate the battery level of each agent. We improve the EKF so that, in addition to gain optimization embedded in the EKF, the motions of agents are controlled to minimize estimation error. Simulation results are presented to demonstrate effectiveness of the proposed method.
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    Coordinated control of an underwater glider fleet in an adaptive ocean sampling field experiment in Monterey Bay
    (Georgia Institute of Technology, 2010) Leonard, Naomi E. ; Paley, David A. ; Davis, Russ E. ; Fratantoni, David M. ; Lekien, Francois ; Zhang, Fumin
    A full-scale adaptive ocean sampling network was deployed throughout the month-long 2006 Adaptive Sampling and Prediction (ASAP) field experiment in Monterey Bay, California. One of the central goals of the field experiment was to test and demonstrate newly developed techniques for coordinated motion control of autonomous vehicles carrying environmental sensors to efficiently sample the ocean. We describe the field results for the heterogeneous fleet of autonomous underwater gliders that collected data continuously throughout the month-long experiment. Six of these gliders were coordinated autonomously for 24 days straight using feedback laws that scale with the number of vehicles. These feedback laws were systematically computed using recently developed methodology to produce desired collective motion patterns, tuned to the spatial and temporal scales in the sampled fields for the purpose of reducing statistical uncertainty in field estimates. The implementation was designed to allow for adaptation of coordinated sampling patterns using human-in-the-loop decision making, guided by optimization and prediction tools. The results demonstrate an innovative tool for ocean sampling and provide a proof of concept for an important field robotics endeavor that integrates coordinated motion control with adaptive sampling.
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    An exploration strategy by constructing Voronoi Diagrams with provable completeness
    (Georgia Institute of Technology, 2009-12) Kim, Jonghoek ; Zhang, Fumin ; Egerstedt, Magnus B.
    We present novel exploration algorithms and a control law that enable the construction of Voronoi diagrams over unknown areas using a single autonomous vehicle equipped with range sensors. Our control law and exploration algorithms are provably complete. The control law uses range measurements to enable tracking Voronoi edges between two obstacles. Exploration algorithms make decisions at vertices of the Voronoi diagram to expand the explored area until a complete Voronoi diagram is constructed in finite time. MATLAB simulation results are provided to demonstrate the effectiveness of both the control law and the exploration algorithms.
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    Curve Tracking for Autonomous Vehicles with Rigidly Mounted Range Sensors
    (Georgia Institute of Technology, 2008-12) Kim, Jonghoek ; Zhang, Fumin ; Egerstedt, Magnus B.
    In this paper, we present a feedback control law to make an autonomous vehicle with rigidly mounted range sensors track a desired curve. In particular, we consider a vehicle which has two range sensors that emit rays perpendicular to the velocity of the vehicle. Under such a sensor configuration, singularities are bound to occur in the feedback control law. Thus, to overcome this, we derive a hybrid strategy of switching between control laws close to the singularity.