UBC Theses and Dissertations
A simulation model for planning and control of forest harvesting operations Bonita, Manuel Libres
This thesis describes a methodology for examining problems associated with the management and control of forest harvesting operations. The methodology developed is one of a systems simulation with general applicability that permits experimentation with a wide class of logging configurations. A model, capable of simulating multi-source, single-sink configurations with variable internode distances, with -various equipment types and combinations, and with various parameters and functional relationships, is described. Written in FORTRAN IV, the model allows independent users to make modifications in the routine to adapt them to the particular operating rules and policies of their operations. The "validity" of the model is tested and demonstrated for an actual West Coast logging division used as a vehicle for model formulation. The verification procedure involves the examination of the assumptions and rules of operation of the model subsystems, and the historical confirmation that for a particular situation the subsystems together make up a system which displays the behavior and characteristics associated with the real system. Some design and tactical considerations in the execution of the model runs are described. Some experimental design problems, together with possible ways of overcoming them, are discussed. In particular, it is shown that the control variate technique can be effectively used with the model to reduce the variance of the difference between two means under comparison. Simulation experiments with various logging configurations indicated the nature of the interrelationships among the responses of the "logging system". These interrelationships are described with respect to a principal factor - the number of trucks in the hauling fleet. Some practical applications of the logging simulation model are discussed and illustrated. The model can be used to evaluate and compare existing operating policies or to formulate new policies. This application is illustrated with reference to the comparison of two operation shutdown modes. The model can also be beneficial in the determination of the equipment requirements of an operation under different operating conditions. Another benefit from the model can be derived from its capability of increasing our understanding of the "logging system" - through learning how the parts of the system behave and interact and through learning how the system responds to changes in its factors. This capability can be beneficial not only in the design of better policies but also in the exercise of better control of the system.
Item Citations and Data