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Xiang S.,Northeastern University China | Zhang Y.,Northeastern University China | Zhang Y.,State Key Laboratory of Robotics | Xia Z.,Northeastern University China | And 2 more authors.
Journal of Computational Information Systems | Year: 2012

DV-Hop location algorithm is very suitable for the application of large-scale sensor network. But it requires the estimation of average hop distance, which lowers down the positioning accuracy. Current popular method is to improve the average hop distance and localization process for unknown nodes through Maximum Likelihood Estimation method or Least Square method. The positioning accuracy of these mentioned methods has been raised. However, it is easy for the position estimation to combine high residual error into the computing process, which will give rise to the localization error along with computational complexity. Considering existent problem, this paper employs Residual Weighting Algorithm to estimate the positions of unknown nodes by improving the calculating mode of average hop distance. For the position estimation with high residual error, we assign a relatively low weight to inhibit its influence. Thus the accuracy and computing process are effectively improved. The experimental results demonstrate that the proposed method can greatly improve the positioning accuracy of unknown nodes, reduce the computational complexity and boost the calculation efficiency. © 2012 Binary Information Press. Source

Guo Y.,Nankai University | Sun M.,Nankai University | Sun M.,State Key Laboratory of Robotics | Garfinkel A.,University of California at Los Angeles | And 2 more authors.
PLoS ONE | Year: 2014

Recent experimental work in lung morphogenesis has described an elegant pattern of branching phenomena. Two primary forms of branching have been identified: side branching and tip splitting. In our previous study of lung branching morphogenesis, we used a 4 variable partial differential equation (PDE), due to Meinhardt, as our mathematical model to describe the reaction and diffusion of morphogens creating those branched patterns. By altering key parameters in the model, we were able to reproduce all the branching styles and the switch between branching modes. Here, we attempt to explain the branching phenomena described above, as growing out of two fundamental instabilities, one in the longitudinal (growth) direction and the other in the transverse direction. We begin by decoupling the original branching process into two semi-independent sub-processes, 1) a classic activator/inhibitor system along the growing stalk, and 2) the spatial growth of the stalk. We then reduced the full branching model into an activator/inhibitor model that embeds growth of the stalk as a controllable parameter, to explore the mechanisms that determine different branching patterns. We found that, in this model, 1) side branching results from a pattern-formation instability of the activator/inhibitor subsystem in the longitudinal direction. This instability is far from equilibrium, requiring a large inhomogeneity in the initial conditions. It successively creates periodic activator peaks along the growing stalk, each of which later on migrates out and forms a side branch; 2) tip splitting is due to a Turing-style instability along the transversal direction, that creates the spatial splitting of the activator peak into 2 simultaneously-formed peaks at the growing tip, the occurrence of which requires the widening of the growing stalk. Tip splitting is abolished when transversal stalk widening is prevented; 3) when both instabilities are satisfied, tip bifurcation occurs together with side branching. © 2014 Guo et al. Source

Zhang Y.-Z.,Northeastern University China | Zhang Y.-Z.,State Key Laboratory of Robotics | Wu C.-D.,Northeastern University China | Cheng L.,Northeastern University China | Ji P.,Northeastern University China
Kongzhi yu Juece/Control and Decision | Year: 2010

The deployment of wireless sensor network in deterministic space with obstacles is researched. Sensor's detection models and coverage quality evaluation are set up. Based on the probabilistic detection model with false alarm rate, a new deployment method is proposed. Watershed algorithm is employed to choose the deploying sub-area. Then Delaunay triangulation is used to generate the candidate positions for new nodes. Thus, the placement of WSN nodes is realized orderly and efficiently. According to the simulation result, the proposed method can attain better detection probability and coverage uniformity compared with different methods such as random deployment, MAX_MIN_COV and MAX_AVG_COV. Source

Wu L.-H.,Dalian Maritime University | Wu L.-H.,State Key Laboratory of Robotics | Xu W.-H.,Dalian Maritime University | Wang L.-P.,Dalian Maritime University
Dalian Haishi Daxue Xuebao/Journal of Dalian Maritime University | Year: 2014

The autonomous underwater vehicle (AUV)underwater terminal docking guidance methods were introduced. With the characteristics of terminal underwater guidance sensors, a ultra short baseline (USBL) combining with a CCD camera was designed. A light source was arranged in dock centerline for vision co-target, with another center point for transponder of USBL. The image coordinates of the light source were obtained through image processing, and the dock position and pose were derived with the known distance between the transponder and the vision source, which can provide the foundation for AUV underwater docking. Source

Wang B.,China Jiliang University | Wang B.,State Key Laboratory of Robotics | Yan D.,China Jiliang University | Fang S.,China Jiliang University | Jin Y.,China Jiliang University
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

In order to ascertain the affect of stiffness on slipping collision of flexible arm, the kinematics model was established by hybrid coordinate method, and flexible deformation was decoupled by using the assumed modes. Contact-impact model was established by using the Hertz impact theory and nonlinear spring-damper theory, collision dynamics of flexible arm was derived through Lagrange equations. The fourth-order Runge-Kutta numerical solution algorithm with variable step-size and precision was designed for solving dynamical equation. Simulation of the impact responses of flexible arm collision under different stiffness were completed, and curves of contact force, joint angle, angle velocity and elastic deformation were given. Based on comparative analysis, with bending stiffness increasing, contact force enlarged and the phase of peak force advanced, the flexible arm joint angle turned smaller, vibration of elastic deformation and angular velocity became lower. Material structural damping had obvious inhibition on the elastic deformation vibration. The model and solving algorithm of this paper are proved effective. Source

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