A Transportation-Scheduling System for Managing Silvicultural Projects

摘要

A silvicultural project encompasses tasks such as site-level planning, regeneration, harvest, and stand-tending treatments. An essential problem in managing silvicultural projects is to efficiently schedule the operations while considering project task due dates and costs of moving scarce resources to specific job locations. Transportation costs represent a significant portion of the total operating cost. The main difficulty in developing such a management system is finding an optimal transport schedule while handling complicated constraints, such as precedence and temporal relations among project tasks, project due dates, truck routing, weather, and other operational conditions. It is well known that finding an optimal solution to these types of problems involves high computational complexity. They are usually NP-hard. For this reason, we propose to use simulated annealing -a meta-heuristic optimization method- that interacts with a network simulation model of the system in which the precedence and temporal relations among project tasks and logistics are explicitly accounted for. The approach has been tested using data provided by a silvicultural contractor located in Alabama. The results obtained solving one instance of a small size problem with five worksites showed that the best solution could be found in less than four minutes using a personal computer with a processor Pentium III (1 GHz). A good solution for a larger problem with twenty worksites was found in thirty minutes. Also a resource analysis is performed to evaluate the impact of each resource on the best solution.