Underactuated leader-follower synchronisation for multi-agent systems with rejection of unknown disturbances

In this paper leader-follower synchronization is considered for underactuated followers in an inhomogeneous multi-agent system. The goal is to synchronise the motion of a leader and an underactuated follower. Measurements of the leader's position and velocity are available, while the dynamics and trajectory of the leader is unknown. The leader velocities are used as input for a constant bearing guidance algorithm to assure that the follower synchronises its motion to the leader. It is also shown that the proposed leader-follower scheme can be applied to multi-agent systems that are subjected to unknown environmental disturbances. Furthermore, the trajectory of the leader does not need to be known. The stability properties of the complete control scheme and the unactuated internal dynamics are analysed using nonlinear cascaded system theory. Simulation results are presented to validate the proposed control strategy.