scholarly journals Energy-Efficient UAV Communication with Multiple GTs Based on Trajectory Optimization

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Yu Xu ◽  
Lin Xiao ◽  
Dingcheng Yang ◽  
Laurie Cuthbert ◽  
Yapeng Wang
Keyword(s):  
Trajectory Optimization ◽  
Low Cost ◽  
High Mobility ◽  
Optimization Techniques ◽  
Mixed Integer ◽  
Flight Trajectory ◽  
Special Cases ◽  
Standard Linear ◽  
Standard Linear Programming

Wireless communications with unmanned aerial vehicles (UAVs) is a promising technology offering potential high mobility and low cost. This paper studies a UAV-enabled communication system, in which a fixed-wing UAV is deployed to collect information from a group of distributed ground terminals (GTs). Considering the requirements for quality of service (QoS) (i.e., the throughput of each GT is above a given threshold) and GT scheduling, we maximize the energy efficiency (EE) of the UAV in bits/Joule by optimizing the UAV’s flight trajectory. In this paper, a mixed integer nonconvex optimization problem is formulated. As that is difficult to solve, we divide the formulated problem into two subproblems and apply standard linear programming (LP) and successive convex optimization techniques. We further propose an efficient iterative algorithm that jointly optimizes GT scheduling and the UAV’s trajectory. Moreover, we set two special cases as benchmarks to measure the performance of the proposed design. The numerical results show that our proposed design achieves much better performance than the other two benchmark designs.

scholarly journals Stable honeycomb structures and temperature based trajectory optimization for wire-arc additive manufacturing

2020 ◽  
Author(s):  
Martin Bähr ◽  
Johannes Buhl ◽  
Georg Radow ◽  
Johannes Schmidt ◽  
Markus Bambach ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Trajectory Optimization ◽  
Tool Path ◽  
Honeycomb Structure ◽  
Mixed Integer ◽  
Voronoi Tesselation ◽  
Integer Linear Programming Problem ◽  
Mathematical Problems ◽  
Wire Arc Additive Manufacturing

Abstract We consider two mathematical problems that are connected and occur in the layer-wise production process of a workpiece using wire-arc additive manufacturing. As the first task, we consider the automatic construction of a honeycomb structure, given the boundary of a shape of interest. In doing this, we employ Lloyd’s algorithm in two different realizations. For computing the incorporated Voronoi tesselation we consider the use of a Delaunay triangulation or alternatively, the eikonal equation. We compare and modify these approaches with the aim of combining their respective advantages. Then in the second task, to find an optimal tool path guaranteeing minimal production time and high quality of the workpiece, a mixed-integer linear programming problem is derived. The model takes thermal conduction and radiation during the process into account and aims to minimize temperature gradients inside the material. Its solvability for standard mixed-integer solvers is demonstrated on several test-instances. The results are compared with manufactured workpieces.

Hamiltonian coordination primitives for decentralized multiagent navigation

2021 ◽  
pp. 027836492110377
Author(s):  
Christoforos Mavrogiannis ◽  
Ross A. Knepper
Keyword(s):  
Trajectory Optimization ◽  
Low Cost ◽  
Trajectory Generation ◽  
Optimization Techniques ◽  
Behavior Prediction ◽  
Multiagent Coordination ◽  
Coordination Strategies ◽  
Online Planning ◽  
Planning Framework ◽  
Gradient Based

We focus on decentralized navigation among multiple non-communicating agents in continuous domains without explicit traffic rules, such as sidewalks, hallways, or squares. Following collision-free motion in such domains requires effective mechanisms of multiagent behavior prediction. Although this prediction problem can be shown to be NP-hard, humans are often capable of solving it efficiently by leveraging sophisticated mechanisms of implicit coordination. Inspired by the human paradigm, we propose a novel topological formalism that explicitly models multiagent coordination. Our formalism features both geometric and algebraic descriptions enabling the use of standard gradient-based optimization techniques for trajectory generation but also symbolic inference over coordination strategies. In this article, we contribute (a) HCP (Hamiltonian Coordination Primitives), a novel multiagent trajectory-generation pipeline that accommodates spatiotemporal constraints formulated as symbolic topological specifications corresponding to a desired coordination strategy; (b) HCPnav, an online planning framework for decentralized collision avoidance that generates motion by following multiagent trajectory primitives corresponding to high-likelihood, low-cost coordination strategies. Through a series of challenging trajectory-generation experiments, we show that HCP outperforms a trajectory-optimization baseline in generating trajectories of desired topological specifications in terms of success rate and computational efficiency. Finally, through a variety of navigation experiments, we illustrate the efficacy of HCPnav in handling challenging multiagent navigation scenarios under homogeneous or heterogeneous agents across a series of environments of different geometry.

scholarly journals Completion Time Minimization for Multi-UAV Information Collection via Trajectory Planning

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 4032 ◽  
Author(s):  
Zhen Qin ◽  
Aijing Li ◽  
Chao Dong ◽  
Haipeng Dai ◽  
Zhengqin Xu
Keyword(s):  
Completion Time ◽  
Low Cost ◽  
High Mobility ◽  
Complete Information ◽  
Mixed Integer ◽  
Information Collection ◽  
Coverage Problem ◽  
Point Selection ◽  
Cycle Cover ◽  
Multi Uav

Unmanned Aerial Vehicles (UAVs) are widely used as mobile information collectors for sensors to prolong the network time in Wireless Sensor Networks (WSNs) due to their flexible deployment, high mobility, and low cost. This paper focuses on the scenario where rotary-wing UAVs complete information collection mission cooperatively. For the first time, we study the problem of minimizing the mission completion time for a multi-UAV system in a monitoring scenario when considering the information collection quality. The mission completion time includes flying time and hovering time. By optimizing the trajectories of all UAVs, we minimize the mission completion time while ensuring that the information of each sensor is collected. This problem can be formulated as a mixed-integer non-convex one which has been proved to be NP-hard. To solve the formulated problem, we first propose a hovering point selection algorithm to select appropriate hovering points where the UAVs can sequentially collect the information from multiple sensors. We model this problem as a BS coverage problem with the information collection quality in consideration. Then, we use a min-max cycle cover algorithm to assign these hovering points and get the trajectory of each UAV. Finally, with the obtained UAVs trajectories, we further consider the UAVs can also collect information when flying and optimize the time allocations. The performance of our algorithm is verified by simulations, which show that the mission completion time is minimum compared with state-of-the-art algorithms.

scholarly journals ScottyActivity: Mixed Discrete-Continuous Planning with Convex Optimization

2018 ◽  
Vol 62 ◽  
pp. 579-664 ◽  
Author(s):  
Enrique Fernandez-Gonzalez ◽  
Brian Williams ◽  
Erez Karpas
Keyword(s):  
Convex Optimization ◽  
Continuous Time ◽  
Trajectory Optimization ◽  
State Of The Art ◽  
Optimization Techniques ◽  
Mixed Integer ◽  
State Variables ◽  
Control Variables ◽  
Model Complex ◽  
And Control

The state of the art practice in robotics planning is to script behaviors manually, where each behavior is typically generated using trajectory optimization. However, in order for robots to be able to act robustly and adapt to novel situations, they need to plan these activity sequences autonomously. Since the conditions and effects of these behaviors are tightly coupled through time, state and control variables, many problems require that the tasks of activity planning and trajectory optimization are considered together. There are two key issues underlying effective hybrid activity and trajectory planning: the sufficiently accurate modeling of robot dynamics and the capability of planning over long horizons. Hybrid activity and trajectory planners that employ mixed integer programming within a discrete time formulation are able to accurately model complex dynamics for robot vehicles, but are often restricted to relatively short horizons. On the other hand, current hybrid activity planners that employ continuous time formulations can handle longer horizons but they only allow actions to have continuous effects with constant rate of change, and restrict the allowed state constraints to linear inequalities. This is insufficient for many robotic applications and it greatly limits the expressivity of the problems that these approaches can solve. In this work we present the ScottyActivity planner, that is able to generate practical hybrid activity and motion plans over long horizons by employing recent methods in convex optimization combined with methods for planning with relaxed plan graphs and heuristic forward search. Unlike other continuous time planners, ScottyActivity can solve a broad class of robotic planning problems by supporting convex quadratic constraints on state variables and control variables that are jointly constrained and that affect multiple state variables simultaneously. In order to support planning over long horizons, ScottyActivity does not resort to time, state or control variable discretization. While straightforward formulations of consistency checks are not convex and do not scale, we present an efficient convex formulation, in the form of a Second Order Cone Program (SOCP), that is very fast to solve. We also introduce several new realistic domains that demonstrate the capabilities and scalability of our approach, and their simplified linear versions, that we use to compare with other state of the art planners. This work demonstrates the power of integrating advanced convex optimization techniques with discrete search methods and paves the way for extensions dealing with non-convex disjoint constraints, such as obstacle avoidance.

CONNECTIVITY IN MOBILE MULTIHOP RELAY NETWORK

2016 ◽  
Vol 78 (5-10) ◽  
Author(s):  
Nurul Nazirah Mohd Imam Ma’arof ◽  
Norsheila Fisal
Keyword(s):  
Relay Selection ◽  
Signal To Noise Ratio ◽  
Low Cost ◽  
Mobile Station ◽  
High Mobility ◽  
Base Station ◽  
Relay Network ◽  
Simulation Tools ◽  
Selection Mechanisms

Mobile Multihop Relay (MMR) network is an attractive and low-cost solution for expanding service coverage and enhancing throughput of the conventional single hop network. However, mobility of Mobile Station (MS) in MMR network might lead to performance degradation in terms of Quality of Service (QoS). Selecting an appropriate Relay Station (RS) that can support data transmission for high mobility MS to enhance QoS is one of the challenges in MMR network. The main goal of the work is to develop and enhance relay selection mechanisms that can assure continuous connectivity while ensuring QoS in MMR network using NCTUns simulation tools. The approach is to develop and enhance a relay selection for MS with continuous connectivity in non-transparent relay. In this approach, the standard network entry procedure is modified to allow continuous connectivity with reduced signaling messages whenever MS joins RS that is out of Multihop Relay Base Station (MRBS) coverage and the relay selection is based on Signal to Noise Ratio (SNR). The QoS performances of the proposed relay selections are in terms of throughput and average end-to-end (ETE) delay. The findings for the proposed relay selection in non-transparent relay shows that the throughput degradation between low mobility MS (30m/s) and high mobility MS (50m/s) is only about 2.0%. The proposed relay selection mechanisms can be applied in any high mobility multi-tier cellular network.

Effect of Computerized Auditory Training on Speech Perception of Adults With Hearing Impairment

2013 ◽  
Vol 20 (3) ◽  
pp. 91-106 ◽  
Author(s):  
Rachel Pizarek ◽  
Valeriy Shafiro ◽  
Patricia McCarthy
Keyword(s):  
Hearing Loss ◽  
Speech Perception ◽  
Literature Review ◽  
Low Cost ◽  
Experimental Designs ◽  
Auditory Training ◽  
Hearing Impairments ◽  
Communicative Disorders ◽  
And Training

Computerized auditory training (CAT) is a convenient, low-cost approach to improving communication of individuals with hearing loss or other communicative disorders. A number of CAT programs are being marketed to patients and audiologists. The present literature review is an examination of evidence for the effectiveness of CAT in improving speech perception in adults with hearing impairments. Six current CAT programs, used in 9 published studies, were reviewed. In all 9 studies, some benefit of CAT for speech perception was demonstrated. Although these results are encouraging, the overall quality of available evidence remains low, and many programs currently on the market have not yet been evaluated. Thus, caution is needed when selecting CAT programs for specific patients. It is hoped that future researchers will (a) examine a greater number of CAT programs using more rigorous experimental designs, (b) determine which program features and training regimens are most effective, and (c) indicate which patients may benefit from CAT the most.

CURRENT SITUATION OF MANAGEMENT AND USE OF TEACHING EQUIPMENT UNDER ORIENTATIONS FOR DEVELOPING STUDENT CAPACITY IN LOWER SECONDARY SCHOOLS IN DIEN BIEN DISTRICT, DIEN BIEN PROVINCE IN THE PRESENT PERIOD

2019 ◽  
Vol 8 (4) ◽  
Author(s):  
Pham Van Phuc ◽  
Ngo Quang Son
Keyword(s):  
Secondary Schools ◽  
Teaching Methods ◽  
Time Management ◽  
Current Trend ◽  
Equipment Management ◽  
Full Time ◽  
Special Cases ◽  
Effective Use ◽  
Lower Secondary Schools

Last time, management of equipment, maintenance and use of teaching equipment in lower secondary schools in Dien Bien district, Dien Bien province has been paid more attention, making important contributions to keeping sustainably, improve the quality of education in the district. Every year the lower secondary schools have been given funding and have plans to equip additional teaching equipment. Most lower secondary schools have full-time staff in charge of teaching equipment; with equipment storage rooms, cabinets are gradually added; laboratories and classrooms have been built more and more; have a system of records of teaching equipment management established; The work of inventorying and purifying teaching equipment periodically was also concerned. The movement of innovating teaching methods has made education managers and teachers more interested in using teaching equipment effectively. The positive management measures have caused many teachers to use teaching equipment as an integral part of the lesson, helping the quality of the lessons be increasingly improved to meet the requirements of changes. New teaching methods. Education administrators, teachers, teaching equipment staff are becoming more and more serious in teaching device management. However, the reality of teaching equipment management still reveals many limitations: The management of teaching equipment in schools is still administrative and ineffective. The equipment has no overall and detailed plans; The procurement of teaching equipment is not guaranteed in terms of quantity, lack of uniformity (some are redundant, some are lacking), quality is limited (durability, accuracy is not guaranteed, some new ones are not used); preservation still has many shortcomings; lack of specialized staff; lack of storage space or insufficient storage; lack of cabinets, prices, laboratories, subject classrooms; specially managing the use of teaching equipment is not tight; Many places teachers have not paid attention to use, ineffective use. The situation of “teaching vegetarianism” is still common, teaching equipment used is still movement, mostly used only in special cases such as competitions for good teachers, lectures or when there is a delegation check; There are many cases of information technology abuse in teaching. The effective use of teaching equipment oriented student capacity development is not much. The management of the use of teaching equipment oriented to develop student competencies in the current trend of Industry Revolution 4.0 is a matter of great concern to educational managers.Thus, the task of surveying the situation of managing the effective use of teaching equipment, finding subjective and objective reasons in order to propose measures to effectively manage the use of teaching equipment in the direction of developing students’ practical capacities and contributing to improving the quality of teaching in secondary schools in Dien Bien district, Dien Bien province is a very important and necessary task today.

The system of indicators of the quality of the carbon-carbon composite materials and technologies of their production

2018 ◽  
pp. 127-132
Author(s):  
T. N. Antipova ◽  
D. S. Shiroyan
Keyword(s):  
Composite Material ◽  
Low Cost ◽  
Experimental Studies ◽  
Carbon Matrix ◽  
Carbon Composite ◽  
Optimal Number ◽  
Laboratory Equipment ◽  
Carbon Composite Material ◽  
Carbon Composite Materials

The system of indicators of quality of carbon-carbon composite material and technological operations of its production is proved in the work. As a result of the experimental studies, with respect to the existing laboratory equipment, the optimal number of cycles of saturation of the reinforcing frame with a carbon matrix is determined. It was found that to obtain a carbon-carbon composite material with a low cost and the required quality indicators, it is necessary to introduce additional parameters of the pitch melt at the impregnation stage.

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