Example 1. Consider an order picking line with 57 bins having
eight pickers in a pick-and-pass system. The related data are listed
in Table 1. A simulation model of the pick-and-pass system based
on the derived analytical model is implemented in Flexsim (2007),
as shown in Fig. 2. The FlexSim is a 3D object-oriented simulation
environment for modeling discrete-event flow processes. A set of
simulation experiments was conducted in order to test the accuracy
of the analytical model. The simulation model calculates the travel
distance of each randomly generated picking location according to
the probabilities that a picker travels to bins. The model was run
1000 times with 500 orders for each picker in the line. The mean
travel distance and standard deviation for each picker are recorded,
and the width of the confidence interval for the travel distance was
assessed at a significance level of 1%. The differences between the
values predicted analytically and the simulation results are displayed
in Table 2, where the difference is expressed as l (the