1,720,972 research outputs found
Simulator software for AGV in industrial environment
No full textThis is a simulation environment where to test different coordination strategies for Automated Guided Vehicles operating in industrial environment. The simulator has been developed in Matlab and it allows to directly load roadmaps designed by a Layout CAD for real applications. The coordination algorithm, which is used for controlling the AGV traffic, can be easily changed in order to simulate the behaviour of the fleet when using different coordination strategies. The actions of each AGV can be changed by an external event in order to simulate unexpected events acting on the fleet
Can molecular dynamics help in understanding dielectric phenomena?
No full textMolecular dynamics (MD) is a modeling technique widely used in material science as well as in chemical physics, biochemistry and biophysics. MD is based on 'first principles', allowing one to compute the physical characteristics of a material, such as density, heat capacity, isothermal compressibility and also the dielectric constant and relaxation, mixing a classical physics approach and statistical mechanics. Although a number of papers exist in the literature concerning the study of the dielectric properties of liquid and solid materials, the MD approach appears to be almost ignored in the electromagnetic aquametry community. We use a rather simple example, a mixture of ethanol and water at various concentrations, to introduce MD as a theoretical tool for investigating the dielectric behavior of more complex moist substances. We show that MD simulations suggest a time-domain model for alcohol-water solutions, consisting in a mixture of a KWW stretched-exponential and a simple exponential, whose validity could be subjected to an experimental verification
Dielectric data analysis: Recovering hidden relaxations by fourth-order derivative spectroscopy
No full textComplex materials exhibit a dielectric behavior that can shed light on their chemophysical structure through a comprehension of the physical mechanisms originating that behavior. For the interpretation of a complex dielectric shape, where multiple relaxations are present (and usually described by semi-empirical functions), a correct interpretation of each simple relaxation is necessary. The separation of often closely overlapped relaxation curves requires the verification of the meaningfulness of such multiple relaxations and to determine their number and relative magnitudes, in other words to resort to a fitting procedure. However, often the physical interpretation of the fitting parameters is not straightforward, and their physical meaning is arguable. The application of even-order derivative spectroscopy is here demonstrated to be able to detect the presence and location of multiple dielectric relaxations, acting on the experimental data without any "a priori" hypothesis
Traffic Management of Automated Guided Vehicles in Flexible Manufacturing Systems
No full textThe objective of the research carried out by Roberto Olmi has been the
development of an innovative traffic management system (TMS) for fleets
of automated guided vehicles (AGV) operating in industrial environments.
These vehicles are used for the transport of materials in environments where
the presence of people and moving machinery has to be expected. The TMS
has to control the motion of the vehicles so as to avoid collisions and optimize
transport times.
The approach is based on the decomposition of the problem into three
parts: assignment of transport tasks, path computation, motion control of
each AGV along its path. Transport orders are assigned to available vehicles
by solving a linear assignment problem through the Jonker Volgenant
algorithm. The objective is to minimize the sum of the times required by
each vehicle to reach the pick station assigned to it. The motion of the
vehicles is defined incrementally by a controller that periodically computes
the list of the trajectory segments that each AGV is allowed to cover. The
sequence of segments is determined so as to minimize the nominal travel
time. In order to define the movement of vehicles along their routes, a tool
called Coordination Diagram (CD) has been applied. Through this instrument,
the problem of coordinating the motion of N AGVs is transformed
into a shortest path problem within an N dimensional space with obstacles.
The main contribution of this dissertation is the application of the CD to
the problem of coordinating a fleet of AGVs in industrial environments. In
[1], [2] and [3], the student has developed an original method to calculate
efficiently the CD. This method is based on an approximation of the CD
that allows to reduce the computational cost of the algorithm and thus
makes it suitable for the coordination of tens of vehicles. To calculate the
shortest path to the CD, in [4] and [5] a complete planning solution has been
proposed that provides greater efficiency with respect to an incremental
approach. However, since the CD changes each time that a path of a vehicle
is modified, an incremental approach is required for the coordination of
AGVs. In particular, in [3] the action that maximizes the advancement of
the fleet while respecting the constraints imposed by the CD is determined
by solving Maximum Independent Set problem. The solver is an heuristic
algorithm which has time complexity quadratic in the number of vehicles
considered.
In order to test the proposed TMS, a simulation software has been developed
using Matlab. The simulations consider AGVs operating on real
layouts developed by Elettric80 S.p.A., a manufacturer of AGV. The proposed
algorithm is much more flexible than the one currently used by the
company. It does not require the manual definition of traffic rules and it
allows a significant savings of time (> 30 days / person) in the construction
of new plants. The research project presented in this dissertation has been
selected as a finalist at the “European Technology Transfer Award 2010”
organized by the associations EUROP(1) and EURON(2).-----
(1) EUROP (www.robotics-platform.eu) is the European Robotics Technology Platform, an industrydriven
framework for the main stakeholders in robotics.
(2) EURON (www.euron.org) is the European Robotics Research Network, a community of more than
200 academic and industrial groups in Europe
A Coordination Technique for Automatic Guided Vehicles in an Industrial Application
No full textIn this paper we propose a methodology for coordinating a group of mobile robots following predefined paths in a dynamic industrial
environment. Coordination diagrams are used for representing the possible collisions among the robots. Exploiting the structure of the
industrial application we are dealing with, we propose an algorithm
for efficiently composing the coordination diagram. Furthermore, we
classify the possible collisions that can take place and the induced
geometry of the resulting coordination diagram. Finally, we exploit
this information for developing a planning algorithm that
allows to coordinate the robots and to take into account unexpected
events that can occur in an industrial environment
Editorial for special section on electromagnetic aquametry
No full textThis special issue of Measurement Science and Technology presents selected contributions from the 11th International Conference on Electromagnetic Wave interaction with Water and Moist Substances (ISEMA) held in Florence, Italy, from 23 to 27 May 2016. The conference was jointly organized by the Institute of Applied Physics of the National Research Council and the Department of Agricultural Sciences of the University of Bologna
Coordinating the motion of multiple AGVs in automatic warehouses
No full textIn this paper an algorithm for planning a coordinated motion of a fleet of Autonomous Guided Vehicles (AGVs)
delivering goods in an automatic warehouse is proposed. The AGVs travel along a common segmented layout and a path
is assigned to each robot by a mission planner. Coordination diagrams are used for representing possible collisions among the robots and a novel algorithm for efficiently determining a coordinated motion of the fleet is proposed. The coordination approach proposed in the paper is validated through experiments on real plants layouts. We present an example in which the coordinated motion of 10 vehicles is computed in only 12.4 sec. on a common PC
A Coordination Technique for Automatic Guided Vehicles in an Industrial Environment
No full text{One of the most challenging steps of a simulation study is the experiments analysis since it provides the information necessary to make decision regarding project objectives. As a matter of fact, a very common practice is to carry out an arbitrary number of simulation runs of arbitrary length and then to perform inference on the simulation results, treating them as the ``true'' model output. The aim of this paper is to propose an innovative methodology to investigate simulation outputs in order to identify ``sustainable target'' for the system and express it as a point value rather than as a confidence interval. For this purpose, a decision support tool is then proposed, it takes as input the process output data of observed samples and provides as result the achievable targets for each couple of replication number and replication length by using the classical statistical concepts of type-I and type-II erro
Coordination of Industrial AGVs
No full textIn this paper, we propose an algorithm for coordinating a group of mobile robots that go through predefined paths in a dynamic industrial environment. Coordination diagrams are used for representing the possible collisions among the vehicles. We exploit this information for developing a centralised and incremental planning algorithm that allows to coordinate the vehicles and to take into account unexpected events that can occur in an industrial environment. Simulation tests have been executed in order to compare the performance of our algorithm with the one currently implemented by the company
A dynamic routing strategy for the traffic control of AGVs in automatic warehouses
No full textIn this paper we propose a novel algorithm for the dynamic routing of a group of Autonomous Guided Vehicles (AGVs) used for transporting goods in automatic warehouses. Our strategy allows to improve the efficiency of a fleet of AGVs in terms of delivery time and its computational burden is sufficiently small to be embedded in standard industrial traffic management system. The algorithm is validated in a small-scale automatic warehouse with real AGVs
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