ABSTRACT
Along with the technological progress, there are more and more things are replaced by machines (Strohmeier et al. 2004). As a result, HumanMachine interaction systems are improved and applied in our lifetime. For instance, Vending Machine (VM) systems have become common equipment. A VM is one kind of machines that can provides various drinks, snacks, beverages, tickets, and other products for all consumers automatically. After paying, a product may become available. In other words, VM brings much convenience in our live. However, it also causes a great deal of consuming dissension once the product or refunding system of one VM gets in trouble. Therefore, how to design one stable product and refunding system in one VM seems an important issue.
