1,721,158 research outputs found
Novel Manufacturing Method of GI Copolymer Optical Fiber Preform and Its Optical Characteristics
No full textNear-time-optimal trajectory planning for wheeled mobile robots with translational and rotational sections
No full textWe derive a near-time-optimal trajectory for wheeled mobile robots (WMRs) satisfying the following: 1) initial and final postures/velocities as well as 2) battery voltage and armature current constraints, under assumptions of simplified dynamics and constant translational/rotational velocity sections. We use a simplified dynamic model for WMRs neglecting inductances of motor armatures and divide our trajectory generation algorithm for cornering motion into three sections, We specify a path-deviation requirement for obstacle avoidance. Transforming dynamics into uncorrelated form with regard to translational and rotational velocities, we make extreme control possible. By splining rotational section with translational sections and determining the velocity scale factor, a near-time-optimal trajectory can be obtained. Simulation results along with inverse control of path-following are given to validate the generated trajectory
Near minimum-time direct voltage control algorithms for wheeled mobile robots with current and voltage constraints
No full textNear minimum-time direct voltage control (DVC) algorithms synthesizing path-planning and path-following are proposed for wheeled mobile robots (WMRs) satisfying (i) initial and final postures and velocities as well as (ii) voltage and current constraints. To overcome nonholonomic and nonlinear properties of WMRs, we divide our control algorithm for cornering motion into three sections: TSD (Translational Section of Deceleration), RS (Rotational Section), and TSA (Translational Section of Acceleration). We developed off-line DVC algorithms using the quadratic problem with the object function minimizing the total time, where voltages to the motors are controlled directly without velocity/torque-servo modules. while satisfying the current constraints. Two methods of searching for the two control parameters (number of steps for RS M(R) and velocity constraint in RS beta) were considered: The one is composed of one simple 1-dimensional search for beta, and the other is composed of two 1-dimensional searches for M(R) and beta which has better performance. Performances of the proposed control algorithms are validated via various simulations
Comparative economic analysis between direct and indirect wiring in the copper-based local loop
No full textIn a copper-based local loop, a circuit pair is indirectly connected to each subscriber usually via a primary cross connection point (PCP) which acts as a buffer to absorb circuit demand fluctuations among subareas. But some telephone operators adhere to the classic practice of direct wiring based on technological preferences without taking advantage of cost-efficient flexibility points. We analyse the extra cost of maintaining the old: practice of direct wiring over the popular one using flexibility points in a single PCP area. For that, the expectation of circuit shortages in subareas during a single replenishment period for the direct wiring is first obtained. Exploiting the convexity of the expectation, we then present a procedure for optimally allocating circuits among subareas, which not only sen es its own purpose of circuit provisioning for the direct wiring but also precisely calculates the extra cost over the indirect case
Experimental investigation on smoke propagation in a transversely ventilated tunnel
No full textIn order to determine the key features of the fire safety design in transversely ventilated tunnels, the smoke propagation characteristics are examined as a function of fire size, fire location, and airflow rates of supply and exhaust. A 12-m long scale model of the Memorial tunnel, with a scale down ratio of cross section 1/20, is used. Fire sizes and ventilation rates in real tunnels are then deduced from the Froude similarity. In general, it is found that the smoke propagating distance increases with the fire size and decreases with the exhaust ventilation rate. When the fire location is off-centered, the propagating distance becomes substantially larger than that of the centered fire with the same size. A hazardous situation generated from an imbalance between the supply rate and the exhaust rate is also observed. The results suggest that the smoke propagating distance and/or the smoke filling may serve as good criteria for determining the transverse ventilation rate
Providing absolute differentiated services for optical burst switching networks: loss differentiation
No full textThe provision of absolute differentiated services for optical burst switching (OBS) networks based on dynamic wavelength assignment is investigated. Unlike existing quality of service (QoS) schemes, such as buffer-based and offset-time based ones, the proposed dynamic virtual lambda partitioning (DVLP) scheme does not mandate any buffer or extra offset time, but can achieve absolute service differentiation between classes. This new DVLP scheme shares wavelength resources based on several different class priorities in an efficient and QoS guaranteed manner. Furthermore, DVLP is robust: this means that each traffic class, with a loss probability conforming to the target value, continues to receive the required QoS, despite the presence of misbehaving packets, such as bursty arrival traffic. The conditions in which the DVLP scheme is feasible are stated, and the performance results are given for the proposed scheme, which effectively guarantees the target loss probability of each traffic class, both in Poisson and self-similar traffic environments.This work was supported in part by the Korea Science and
Engineering Foundation (KOSEF) through the OIRC
projec
Input and system identification of the Hualien soil-structure interaction system using earthquake response data
No full textThis paper presents an input and system identification technique for a soil-structure interaction system using earthquake response data. Identification is carried out on the Hualien large-scale seismic test structure, which was built in Taiwan for international joint research. The identified quantities are the input ground acceleration as well as the shear wave velocities of the near-field soil regions and Young's moduli of the shell sections of the structure. The earthquake response analysis on the soil-structure interaction system is carried out using the finite element method incorporating the infinite element formulation for the unbounded layered soil medium and the substructured wave input technique. The criterion function for the parameter estimation is constructed using the frequency response amplitude ratios of the earthquake responses measured at several points of the structure, so that the information on the input motion may be excluded. The constrained steepest descent method is employed to obtain the revised parameters. The simulated earthquake responses using the identified parameters and input ground motion show excellent agreement with the measured responses. Copyright 0 2003 John Wiley Sons, Ltd
Visual servo control algorithm for soccer robots considering time-delay
No full textAn efficient visual servo control algorithm which uses primary/secondary controller and the Smith predictor based an an accurate model of robot soccer system including time-delay is suggested for micro-robot soccer tournament (MIROSOT). In this paper, we analyze and design control system of soccer robot in the frame of visual servoing. We think that our approach encourages more systematic approaches to soccer robot system. MIROSOT system is a typical direct visual servo system with a fixed camera and mobile robots with internal sensors such as encoders. In real games, encoders often offer wrong position data due to slips and collisions between robots or between a robot and a walt However, vision provides positions and orientations of robots in certain accuracy regardless of slips or collisions. In spite of this advantage inevitable time-delay arising from vision and communication subsystems seriously causes undesired effects in control of robots. In this paper we present a visual servo controller considering the time-delay. First, we present an accurate dynamic model of organic cooperation of robot soccer systems [3] that includes the time-delay. And we design the Smith predictor [13] using the model to cancel out the deteriorating effect of time-delay in our soccer robot system And using the model, we also propose control structure with primary/secondary controller [12] to control the system precisely. Finally, we show performance of the proposed controller and the predictor in simulation studies
RDF version of the data from Choi, JS. et al. Towards a generalized toxicity prediction model for oxide nanomaterials using integrated data from different sources (2018)
No full textThis is an RDFied version of the dataset published in Choi, JS., Ha, M.K., Trinh, T.X. et al. Towards a generalized toxicity prediction model for oxide nanomaterials using integrated data from different sources. Sci Rep 8, 6110 (2018)
The original dataset publication DOI: https://doi.org/10.1038/s41598-018-24483-z
The Original publication authors: Jang-Sik Choi, My Kieu Ha, Tung Xuan Trinh, Tae Hyun Yoon & Hyung-Gi Byu
Earthquake Response Analysis of a Large Scale Seismic Test Structure Using Updated Soil-Structure Propertied
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