Attitude tracking control of a 3-DOF helicopter with actuator saturation and model uncertainties

A novel attitude tracking control methodology of a 3-DOF helicopter is presented in the presence of actuator saturation and model uncertainties. The proposed control approach consists of an unconstrained controller and a nonlinear anti-windup compensator (AWC). The backstepping control technique is first applied to the unconstrained controller to achieve the tracking control objective for the nominal nonlinear model of the helicopter. Then, a nonlinear disturbance observer is proposed to estimate the parametric uncertainties and external disturbances. The globally uniformly ultimately boundedness of the unconstrained controller is illustrated through theoretical analysis. Finally, to deal with the actuator saturation, a nonlinear AWC is derived, which simultaneously guarantees a region of stability and the closed loop performance for tracking control. Simulation results on the 3-DOF helicopter verify the effectiveness of the proposed method.