Hello,
My name is Ted. I am a graduate student of National Cheng Kung University in Taiwan. I am trying to model “capacity tightness” into a traditional beer distribution model with some modifications. The capacity tightness indicates the ratio of total available capacity to total capacity needed (i.e. Total available capacity equals to CT multiply by total capacity needed). There is no capacity constraint in the initial conditions of a board beer game. I must begin with adding a capacity sector to the original beer game model.
The stock variable “CAPACITY” level will be adjusted according to the auxiliary variable “production requests” and the “adjustment time” (e.g. [“production requests”-“capacity”] / “adjustment time”). I add an auxiliary variable “available to production” which is formulated as the following equation:
IF THEN ELSE ("Production Requests"<=Capacity, "Production Requests", Capacity)
So, the production rate will be regulated by the order flow (production request) and the available capacity that factory possessed this period.
Auxiliary variable “order unfilfullment” is calculated as “production request” minus “available to production” and it will influence the inflow of another stock variable “BACKLOG”. The original auxiliary variable “production rate” is equal to “available to production”.
I am not sure whether this method is appropriated (or at least reasonable) for modeling capacity constraint, but I try to make my model as simply as possible.
The behavior of the system (each layer’s inventory) is dramatically oscillatory and never achieves equilibrium. General speaking, a capacity constraint may impact the dynamics but will not change their general character unless it is very constraining.
I don’t know what is wrong with my model. the new variable "available to production" seems to be the key point of the problem. Could there anybody give me some advice about how to modeling capacity constraint? Thanks for your time and reading my problem.
Regards,