I. Introduction
Multiagent coordination has been a hot topic over the last decade due to its wide applications in engineering systems. Particularly, steering agents to a prescribed pattern is widely studied in different circumstances. In this type of problems, a (virtual) leader is often set up to describe this pattern or generate references for other agents to follow, while the leader is usually given as a known autonomous dynamic system with possible unknown states. Many results embodying this idea have been obtained in both theoretical and engineering sides (see [1]–[5] and references therein).