Feedforward Control for Wind Rejection in Fixed-Wing UAVs

This paper presents a modular feedforward wind rejection method for agile fixed-wing UAVs, designed to work in tandem with a thrust pointing position controller. The feedforward controller requires a trustworthy wind estimate, and is based on three components, a feedforward rotation on attitude and two feedforward components on thrust. The controller uses attitude trim conditions to reject wind disturbances near the cross-wind condition, while also adopting an airspeed-based feedforward on thrust to reduce disturbances when flying in-line with the wind vector. The feedforward controller was validated in simulation and outdoor flight tests. Simulated flights consisted of straight line and circular tracking in a constant wind-field, as well as frequency tests to examine the ability of the feedforward controller to reject wind fluctuations. Experimental flight tests tracking a circular path in a windy environment were conduced. The results of simulations and experimental flights show that the feedforward controller provides good wind rejection performance when compared to the feedback position controller operating on its own.