Lee, Moonsu (2005-05). Analytical models to evaluate system performance measures for vehicle based material-handling systems under various dispatching policies. Doctoral Dissertation. Thesis uri icon

abstract

  • Queueing network-based approximation models were developed to evaluate the performance of fixed-route material-handling systems supporting a multiple workcenter manufacturing facility. In this research, we develop analytical models for fixed-route material-handling systems from two different perspectives: the workcenters?? point of view and the transporters?? point of view. The state-dependent nature of the transportation time is considered here for more accurate analytical approximation models for material-handling systems. Also, an analytical methodology is developed for analytical descriptions of the impact of several different vehicledispatching policies for material-handling systems. Two different types of vehicledispatching policies are considered. Those are workcenter-initiated vehicle dispatching rules and vehicle-initiated vehicle dispatching rules. For the workcenterinitiated vehicle dispatching rule, the Closest Transporter Allocation Rule (CTAR) was used to assign empty transporters to jobs needing to be moved between various workcenters. On the other hand, four different vehicle-initiated vehicle dispatching rules, Shortest Distance Dispatching Rule (SDR), Time Limit/Shortest DistanceDispatching Rule (TL/SDR), First-Come First-Serve Dispatching Rule (FCFSR), Longest Distance Dispatching Rule (LDR), are used to select job requests from workcenters when a transporter is available. From the models with a queue space limit of one at each workcenter and one transporter, two different types of extensions are considered. First, the queue space limit at each workcenter is increased from one to two while the number of transporters remains at one. Second, the number of transporters in the system is also increased from one to two while maintaining the queue space limit of one at each workcenter. Finally, using a simulation approach, we modified the Nearest Neighbor (NN) heuristic dispatching procedure for multi-load transporters proposed by Tanchoco and Co (1994) and tested for a fixed-route material-handling system. The effects of our modified NN and the original NN transporter dispatching procedures on the system performance measures, such as WIP or Cycle Time were investigated and we demonstrated that the modified NN heuristic dispatching procedure performs better than the original NN procedure in terms of these system performance measures.
  • Queueing network-based approximation models were developed to evaluate
    the performance of fixed-route material-handling systems supporting a multiple
    workcenter manufacturing facility. In this research, we develop analytical models for
    fixed-route material-handling systems from two different perspectives: the
    workcenters?? point of view and the transporters?? point of view. The state-dependent
    nature of the transportation time is considered here for more accurate analytical
    approximation models for material-handling systems. Also, an analytical methodology
    is developed for analytical descriptions of the impact of several different vehicledispatching
    policies for material-handling systems. Two different types of vehicledispatching
    policies are considered. Those are workcenter-initiated vehicle
    dispatching rules and vehicle-initiated vehicle dispatching rules. For the workcenterinitiated
    vehicle dispatching rule, the Closest Transporter Allocation Rule (CTAR)
    was used to assign empty transporters to jobs needing to be moved between various
    workcenters. On the other hand, four different vehicle-initiated vehicle dispatching
    rules, Shortest Distance Dispatching Rule (SDR), Time Limit/Shortest DistanceDispatching Rule (TL/SDR), First-Come First-Serve Dispatching Rule (FCFSR),
    Longest Distance Dispatching Rule (LDR), are used to select job requests from
    workcenters when a transporter is available. From the models with a queue space limit
    of one at each workcenter and one transporter, two different types of extensions are
    considered. First, the queue space limit at each workcenter is increased from one to
    two while the number of transporters remains at one. Second, the number of
    transporters in the system is also increased from one to two while maintaining the
    queue space limit of one at each workcenter. Finally, using a simulation approach, we
    modified the Nearest Neighbor (NN) heuristic dispatching procedure for multi-load
    transporters proposed by Tanchoco and Co (1994) and tested for a fixed-route
    material-handling system. The effects of our modified NN and the original NN
    transporter dispatching procedures on the system performance measures, such as WIP
    or Cycle Time were investigated and we demonstrated that the modified NN heuristic
    dispatching procedure performs better than the original NN procedure in terms of
    these system performance measures.

publication date

  • May 2005