Continuous-Time Models for Estimating Picker Blocking in Order-Picking-Systems

Congestion is a problem in order-picking-systems. We developed CTMC models to represent picker blocking in cases including pickers with different exponentially distributed picking times and k pickers, for narrow and wide aisle systems. The focus was not to produce an all-inclusive model, but to generate models that give designers insight of the system, allowing them to reduce the number of variables considered. We ran instances with various parameters and validated the models against simulation. We found stochastic speeds generate more blockage that deterministic ones, differences in pickers cause more congestion, systems with k pickers are more complex and have greater blockage.