“…However, most of these papers only focus on so-called unconstrained consensus applications. When the consensus, that the system is to reach, should fulfil external conditions (such as a common heading of a flock of agents, but in a particular direction), three approaches are usually taken, see Beard et al (2001), Lawton et al (2003), Ren and Beard (2004) and citations therein: leader-following (Wang 1989, Singh et al 2000, Mesbahi and Hadaegh 1999, Fax and Murray 2004, Ji et al 2006, virtual structure based (Lewis and Tan 1997, Beard et al 2000, Shi et al 2005 or behaviour based (Balch and Arkin 1998, Anderson and Robbins 1998, Lawton et al 2003, Parker 1998, Chen and Luh 1994, Veloso et al 2000 approaches. The first concept presents a common technique used typically to make formations of autonomous mobile agents follow desired trajectories.…”