Person:
Zhang, Fumin

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Now showing 1 - 7 of 7
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    Intruder Capturing Game on a Topological Map Assisted by Information Networks
    (Georgia Institute of Technology, 2011-12) Kim, Jonghoek ; Maxon, Sean ; Egerstedt, Magnus B. ; Zhang, Fumin
    Intruder capturing games on a topological map of a workspace with obstacles are investigated. Assuming that a searcher can access the position of any intruder utilizing information networks, we provide theoretical upper bounds for the minimum number of searchers required to capture all intruders on a Voronoi graph. Intruder capturing algorithms are proposed and demonstrated through an online computer game.
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    Diagnosis and Prognosis of Scrubber Faults for Underwater Rebreathers based on Stochastic Event Models
    (Georgia Institute of Technology, 2011-06) Chang, Dongsik ; Zhang, Fumin ; West, Michael
    Imperfect CO₂ removal mechanisms of CO₂ scrubbers often lead to the existence of CO₂ in gas inhaled by a diver from underwater rebreathers. This may cause CO₂ related rebreather faults and subsequently would increase the risk of human injuries. We introduce a stochastic model for three CO₂ related rebreather faults: CO₂ bypass, scrubber exhaustion, and scrubber breakthrough. We establish the concept of CO₂ channeling that describes the cause of the faults and present a CO₂ channeling model based on a stochastic process driven by a Poisson counter. This helps us to investigate how CO₂ flow inside the rebreather is affected by CO₂ related faults. Fault diagnosis/prognosis algorithms are developed based on the stochastic model and are tested in simulation.
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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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    Robust Control of Horizontal Formation Dynamics for Autonomous Underwater Vehicles
    (Georgia Institute of Technology, 2011) Yang, H. ; Zhang, Fumin
    This paper presents a novel robust controller design for formation control of autonomous underwater vehicles (AUVs). We consider a nonlinear three-degree-of-freedom dynamic model for the horizontal motion of each AUV. By using the Jacobi transform, the horizontal dynamics of AUVs are explicitly expressed as dynamics for formation shape and formation center, and are further decoupled by feedback control. We treat the coupling terms as perturbations to the decoupled system. An H_inf state feedback controller is designed to achieve robust stability of the closed loop formation and translation dynamics. By incorporating an orientation controller, the formation shape under control converges and the formation center tracks a desired trajectory simultaneously. Simulation results demonstrate the effectiveness of the controllers.
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    Experimental Validation of Source Seeking with a Switching Strategy
    (Georgia Institute of Technology, 2011) Wu, Wencen ; Zhang, Fumin
    We design a switching strategy for a group of robots to search for a local minimum of an unknown noisy scalar field. Starting with individual exploration, the robots switch to cooperative exploration only when they are not able to locate the field minimum based on the information collected individually. In order to test and demonstrate the switching strategy in real-world environment, we implement the switching strategy on a multi-robot test-bed. The behaviors of a group of robots are compared when different parameters for exploration are adopted. Especially, we observe the effect of memory lengths on the switching behaviors as predicted by theoretical results. The experimental results also justify the effects of different formation sizes and noise attenuation levels on the performance of the cooperative H∞ filter that are utilized in the cooperative exploration phase.
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    Input-to-State Stability for Curve Tracking Control: A Constructive Approach
    (Georgia Institute of Technology, 2011) Malisoff, Michael ; Mazenc, Frédéric ; Zhang, Fumin
    We analyze an important class of feedback controllers for curve tracking problems for robotics. Earlier experimental work suggested the robust performance of the control laws under perturbations. In this note, we use input-tostate stability to prove predictable tolerance and safety bounds that guarantee robust performance. Our work uses an invariant polygon argument and a new strict Lyapunov function design. We demonstrate our findings in simulations.
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    Steady three dimensional gliding motion of an underwater glider
    (Georgia Institute of Technology, 2011) Zhang, Shaowei ; Yu, Jiancheng ; Zhang, Aiqun ; Zhang, Fumin
    Underwater Gliders have found broad applications in ocean sampling. In this paper, the nonlinear dynamic model of the glider developed by the Shenyang Institute of Automation, Chinese Academy of Sciences, is established. Based on this model, we solve for the parameters that characterize steady state spiraling motions of the glider. A set of nonlinear equations are simplified so that a recursive algorithm can be used to find the solutions.