A small robot with a clip-like hand and enough smarts to know which drinks are popular is part of an effort to make convenience stores even more convenient. On a recent day in Tokyo, the robot named TX SCARA slid back and forth behind the refrigerated shelves in the back of a FamilyMart store. The hand on the end of its mechanical arm grasped a bottle or can from the stacks to the side, then the robot slithered to the right spot and placed the drink on the shelf -- in a place chosen after its artificial intelligence and tiny cameras matched the kind of beverage to what's running short. TX SCARA is filling a needed role in Japan's "conbini," as the ubiquitous tiny stores selling snacks, drinks and knick-knacks are called. Most such stores are open 24-seven, filled with 3,000 kinds of products, but have relatively few workers.