Helicopter hovering attitude control using a direct feedthrough simultaneous state and disturbance observer

Helicopters are frequently required to operate in adverse conditions where they are likely to encounter unknown force disturbances due to aerodynamic effects, such as wind and ground effect. To maintain helicopter stability, these disturbances must be accurately estimated and compensated for. In this paper, a novel linear direct feedthrough simultaneous state and disturbance observer is postulated. A combination of state feedback and disturbance feedback control is then used to stabilise helicopter attitude, where the observer and controller gains are obtained using H_∞ synthesis. Simulated results for a Yamaha R-50 helicopter demonstrate that a direct feedthrough simultaneous state and disturbance observer-based control system can accurately estimate helicopter states and unknown force disturbances and can stabilise helicopter attitude and velocity in the presence of unknown disturbances.