Scheduling variable processing time operations in systems with buffers

In this work a scheduling operation problem with variable processing times is analysed. In particular this project is concerned with the scheduling of the truck load operations and the preparation of loads in buffers in an automatic warehouse. The truck load operations can be assumed as processing tasks with ready times (availability of the trucks) and due dates (trip cut off time). Additionally, it is possible to process a task before ready time by using a buffer where a truck load is assembled to be transferred to the truck in a later time period. Processing time is variable and depends upon the number of tasks simultaneously in progress. A minimum number of simultaneous tasks is assumed in order to guarantee a maximum, nominal, rate of progress. A procedure based on Dynamic Programming with truck expedition times ordered by EDD rule is presented. The algorithm efficiency is also discussed.