2134/11130 Cunjia Liu Cunjia Liu Wen-Hua Chen Wen-Hua Chen J.D. Andrews J.D. Andrews Tracking control of small-scale helicopters using explicit nonlinear MPC augmented with disturbance observers Loughborough University 2012 Model predictive control Disturbance observer Trajectory tracking Helicopter Flight test Mechanical Engineering Engineering not elsewhere classified 2012-12-07 13:29:47 Journal contribution https://repository.lboro.ac.uk/articles/journal_contribution/Tracking_control_of_small-scale_helicopters_using_explicit_nonlinear_MPC_augmented_with_disturbance_observers/9226745 Small-scale helicopters are very attractive for a wide range of civilian and military applications due to their unique features. However, the autonomous flight for small helicopters is quite challenging because they are naturally unstable, have strong nonlinearities and couplings, and are very susceptible to wind and small structural variations. A nonlinear optimal control scheme is proposed to address these issues. It consists of a nonlinear model predictive controller (MPC) and a nonlinear disturbance observer. First, an analytical solution of the MPC is developed based on the nominal model under the assumption that all disturbances are measurable. Then, a nonlinear disturbance observer is designed to estimate the influence of the external force/torque introduced by wind turbulences, unmodelled dynamics and variations of the helicopter dynamics. The global asymptotic stability of the composite controller has been established through stability analysis. Flight tests including hovering under wind gust and performing very challenging pirouette have been carried out to demonstrate the performance of the proposed control scheme.