I sincerely hope that you can help me with some issues that I have trying to use Vensim optimization tool for my employee´s scheduling activity model.
Briefly, the situation is this: I´m doing a simulation model for my thesis about a process done in an invented factory. Here, there are some activities that should be terminated sequentially to finally complete the job. The rate in which the activity can be completed depend in how many employees are assigned to work in it. My purpose is then optimizing the way how the employee´s assignation to each activity should be done, taking into account that there is a limited number of employees for the whole job.
I have two main problems: 1) the total available employees for the job become negative!! (I tried conditionals, built-in range options, and cannot avoid the issue). 2) I cannot minimize the backlogs of all the activities because there are not available parameters to use in the optimization tool.
I attach my simulation model, but since I live in Colombia (South America) and the model is in Spanish, I´d colored the most important variables so I can explain them quickly: The level in red is the total available employees for the whole job. The levels in orange represent the employees that are assigned in each activity. The blue auxiliary variables represent the “backlog” of each activity measured as the percentage of the work needed to be done at the each activity over the total work for that activity (works through a lookup function colored as gray variables). The green variables are the ideal number of employees that are supposed to be working in each activity depending on its percentage of “backlog”. Since the needs change in time there is a gap between the ideal number and the already working employees (called “Brecha”) that determines the flows of assigning workers to activities.
So regarding my 2 issues:
For the first, the level in red becomes negative meaning I have negative available workers!!
For the second, I try to minimize the backlog percentage of each activity (gray variables) trying to change the lookup function that determines the ideal number of workers in each activity.
Please if you have any suggestions for my 2 issues, I will be very grateful
.Felipe Venegas