287 research outputs found
A Multi-Objective Genetic Algorithm for the Vehicle Routing with Time Windows and Loading Problem
This work presents the Vehicle Routing with Time Windows and Loading Problem (VRTWLP) as a multi-objective optimization problem, implemented within a Genetic Algorithm. Specifically, the three dimensions of the problem to be optimized – the number of vehicles, the total travel distance and volume utilization – are considered to be separated dimensions of a multi-objective space. The quality of the solution obtained using this approach is evaluated and compared with results of other heuristic approaches previously developed by the author. The most significant contribution of this work is our interpretation of VRTWLP as a Multi-objective Optimization Problem
A Heuristic Approach to the Theater Distribution Problem
Analysts at USTRANSCOM are tasked with providing vehicle mixtures that will support the distribution of requirements as provided in the form of TPFDD. An integer programming model exists to search for optimal solutions to these problems, but it is fairly time consuming, and produces only one of potentially several good quality solutions. This research constructs a number of heuristic approaches to solving the TDP. Two distinct shipping methods are examined and applied through both constructive and probabilistic vehicle assignment processes. Multistart metaheuristic approaches are designed and used in conjunction with the constructive and probabilistic approaches. Random TPFDDs of size 20, 100 and 1000 are tested, and solutions are compared to those obtained by the integer programming approach. The heuristic models implemented in this research develop feasible solutions to the notional TPFDDs in less time than the integer program. They can very quickly identify a number of good quality solutions to the same problem
Exploring Heuristics for the Vehicle Routing Problem with Split Deliveries and Time Windows
This dissertation investigates the Vehicle Routing Problem with Split Deliveries and Time Windows. This problem assumes a depot of homogeneous vehicles and set of customers with deterministic demands requiring delivery. Split deliveries allow multiple visits to a customer and time windows restrict the time during which a delivery can be made. Several construction and local search heuristics are tested to determine their relative usefulness in generating solutions for this problem. This research shows a particular subset of the local search operators is particularly influential on solution quality and run time. Conversely, the construction heuristics tested do not significantly impact either. Several problem features are also investigated to determine their impact. Of the features explored, the ratio of customer demand to vehicle ratio revealed a significant impact on solution quality and influence on the effectiveness of the heuristics tested. Finally, this research introduces an ant colony metaheuristic coupled with a local search heuristic embedded within a dynamic program seeking to solve a Military Inventory Routing Problem with multiple-customer routes, stochastic supply, and deterministic demand. Also proposed is a suite of test problems for the Military Inventory Routing Problem
A Hybrid Heuristic for a Broad Class of Vehicle Routing Problems with Heterogeneous Fleet
We consider a family of Rich Vehicle Routing Problems (RVRP) which have the
particularity to combine a heterogeneous fleet with other attributes, such as
backhauls, multiple depots, split deliveries, site dependency, open routes,
duration limits, and time windows. To efficiently solve these problems, we
propose a hybrid metaheuristic which combines an iterated local search with
variable neighborhood descent, for solution improvement, and a set partitioning
formulation, to exploit the memory of the past search. Moreover, we investigate
a class of combined neighborhoods which jointly modify the sequences of visits
and perform either heuristic or optimal reassignments of vehicles to routes. To
the best of our knowledge, this is the first unified approach for a large class
of heterogeneous fleet RVRPs, capable of solving more than 12 problem variants.
The efficiency of the algorithm is evaluated on 643 well-known benchmark
instances, and 71.70\% of the best known solutions are either retrieved or
improved. Moreover, the proposed metaheuristic, which can be considered as a
matheuristic, produces high quality solutions with low standard deviation in
comparison with previous methods. Finally, we observe that the use of combined
neighborhoods does not lead to significant quality gains. Contrary to
intuition, the computational effort seems better spent on more intensive route
optimization rather than on more intelligent and frequent fleet re-assignments
Internet of Things in urban waste collection
Nowadays, the waste collection management has an important role in urban areas. This paper faces this issue and proposes the application of a metaheuristic for the optimization of a weekly schedule and routing of the waste collection activities in an urban area. Differently to several contributions in literature, fixed periodic routes are not imposed. The results significantly improve the performance of the company involved, both in terms of resources used and costs saving
Enhanced Iterated local search for the technician routing and scheduling problem
Most public facilities in the European countries, including France, Germany,
and the UK, were built during the reconstruction projects between 1950 and
1980. Owing to the deteriorating state of such vital infrastructure has become
relatively expensive in the recent decades. A significant part of the
maintenance operation costs is spent on the technical staff. Therefore, the
optimal use of the available workforce is essential to optimize the operation
costs. This includes planning technical interventions, workload balancing,
productivity improvement, etc. In this paper, we focus on the routing of
technicians and scheduling of their tasks. We address for this purpose a
variant of the workforce scheduling problem called the technician routing and
scheduling problem (TRSP). This problem has applications in different fields,
such as transportation infrastructure (rail and road networks),
telecommunications, and sewage facilities. To solve the TRSP, we propose an
enhanced iterated local search (eILS) approach. The enhancement of the ILS
firstly includes an intensification procedure that incorporates a set of local
search operators and removal-repair heuristics crafted for the TRSP. Next, four
different mechanisms are used in the perturbation phase. Finally, an elite set
of solutions is used to extensively explore the neighborhood of local optima as
well as to enhance diversification during search space exploration. To measure
the performance of the proposed method, experiments were conducted based on
benchmark instances from the literature, and the results obtained were compared
with those of an existing method. Our method achieved very good results, since
it reached the best overall gap, which is three times lower than that of the
literature. Furthermore, eILS improved the best-known solution for
instances among a total of while maintaining reasonable computational
times.Comment: Submitted manuscript to Computers and Operations Research journal. 34
pages, 7 figures, 6 table
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