A Control-Equivalent-Turbulence-Input estimation method for unmanned helicopters

This paper describes a new time-domain estimation method of the Control Equivalent Turbulence Input (CETI). CETI simulates the effects of natural atmospheric turbulence on rotorcraft dynamics by additional control inputs. The identified linear model of helicopter dynamics is changed into a quasi-nonlinear model by adding trim data and nonlinear kinematic equations. An unscented Kalman filter is designed using the quasi-nonlinear helicopter model and scaled unscented transformation to estimate CETI in real-time. The method was first tested in simulations; then, results were obtained for flight. The proposed method is also compared with other methods used in practice.