Robust Second-Order Consensus Tracking of Multiple 3-DOF Laboratory Helicopters via Output Feedback

The second-order consensus tracking problem of multiple 3-degree-of-freedom laboratory helicopters is studied on directed communication topologies in this paper. The laboratory helicopters are subjected to nonlinearity, model uncertainty, and equipped only with angular position sensors. We present a decentralized consensus controller that includes a nonlinear uncertainty and disturbance estimation (UDE) term to compensate the model uncertainties and disturbances in each vehicle and its neighborhood. The UDE term consists of a second-order auxiliary system and a discontinuous term, neither the measurement of angular velocity nor its asymptotic estimation is required. Convergence of the tracking error is analyzed using invariance-like theorems. It is also proved that the UDE term will converge to the actual uncertainties and disturbances. Experimental results show that a group of four vehicles reach second-order consensus tracking using the proposed method, on a one-direction communication topology where only one vehicle can reach the reference signal.