Separate-Channel Integrated Guidance and Autopilot for Automatic Path-Following

An integrated guidance and autopilot scheme for a path-following uninhabited aerial vehicle is presented in this study. A fixed-wing aircraft usually performs a bank-to-turn maneuver to change its flight direction. The novel approach presented here, however, assumes that each of the three channels of the integrated guidance and autopilot can be independently designed. This concept makes the design process simple. A virtual target moving on the prespecified path for the uninhabited aerial vehicle is introduced to facilitate the algorithm development. A first-/second-order sliding structure with a second-order sliding mode and a high-order sliding mode differentiator for the estimation of the uncertain sliding surfaces are selected to develop the uninhabited aerial vehicle's integrated guidance and autopilot scheme. Stability analysis and error bounds due to measurement errors and model uncertainties are provided. The potential of the proposed method is demonstrated through a path-following application of an uninhabited aerial vehicle on a difficult helical ascent flight under wind turbulence.