Simulation or Optimization?

[Nirmala]

Hi there,
I wish to find the optimal number of trucks required in my facility to move raw material as well as finished goods. Which tools would you suggest to use?

[ewilliams]

Excellent question. Simulation and optimization are not mutually exclusive. I would begin with simulation, since it seems very likely you will have many sources of variation (e.g., truck breakdowns and maintenance, load and unload time variability, and variability in market demand for various products the trucks might move, to name just three). You likely also have multiple tempting performance metrics -- possibilities such as service quality (e.g., average and maximum wait times for pickup) to the raw-material moves, service quality to the finished-goods moves, capital investment cost of the trucks, operating cost of the trucks, and inventory levels. Simulation is more adaptable to (a) different objectives explored concurrently and to (b) incorporating the sources of variation into the analysis. An example of (a) is "Shall we minimize wait times under a cost constraint or minimize cost under a wait time constraint?" A simulation analysis can do each of these and more in rapid succession.

[rwilcox]

Given that this thread leans toward doing simulation instead of optimization (or, at least, beginning with simulation), what simulation software package would you recommend, given that trucks must travel a network of defined routes? Thanks

[ewilliams]

Given that the trucks will be traveling a network (defined paths and nodes), ED, AutoMod, and ProModel are good choices to consider; all have a powerful and user-friendly interface for defining such material-handling networks.

[kvasudevan]

I agree to the above comment. However my experience of using Advanced transporters in ED has not been fruitful. This atom in ED needs to be further developed and tested. There are random failures in this atom relating to input and output channels that led to an extened development time even for a demo model.
However, ED has just released a Winter update, and these bugs may have well been fixed.