Vehicle chaining phenomenon in a unidirectional circular transport system

We investigate an interesting vehicle chaining phenomenon observed from the dynamics of automated vehicles in 300 mm semiconductor manufacturing. This paper explores the causes of this phenomenon and clarifies its impacts on job waiting time. We first start from a simple case where there are only two vehicles in a loop. We then extends to the general problem with multiple vehicles in a unidirectional circular loop. Computer simulations are then conducted to demonstrate this phenomenon. Statistical analysis of simulation results shows that the average waiting times are significantly independent of number of vehicles in the loop.