Acceleration based manoeuvre flight control system for unmanned aerial vehicles

[摘要] A strategy for the design of an effective, practically feasible, robust, computationally efficientautopilot for three dimensional manoeuvre flight control of Unmanned Aerial Vehicles ispresented. The core feature of the strategy is the design of attitude independent inner loopacceleration controllers. With these controllers implemented, the aircraft is reduced to a pointmass with a steerable acceleration vector when viewed from an outer loop guidanceperspective. Trajectory generation is also simplified with reference trajectories only requiredto be kinematically feasible. Robustness is achieved through uncertainty encapsulation anddisturbance rejection at an acceleration level.The detailed design and associated analysis of the inner loop acceleration controllers is carriedout for the case where the airflow incidence angles are small. For this case it is shown thatunder mild practically feasible conditions the inner loop dynamics decouple and becomelinear, thereby allowing the derivation of closed form pole placement solutions. Dimensionaland normalised non-dimensional time variants of the inner loop controllers are designed andtheir respective advantages highlighted. Pole placement constraints that arise due to thetypically weak non-minimum phase nature of aircraft dynamics are developed.A generic, aircraft independent guidance control algorithm, well suited for use with the innerloop acceleration controllers, is also presented. The guidance algorithm regulates the aircraftabout a kinematically feasible reference trajectory. A number of fundamental basis trajectoriesare presented which are easily linkable to form complex three dimensional manoeuvres.Results from simulations with a number of different aircraft and reference trajectories illustratethe versatility and functionality of the autopilot.Key words: Aircraft control, Autonomous vehicles, UAV flight control, Acceleration control,Aircraft guidance, Trajectory tracking, Manoeuvre flight control.

[发布机构] Stellenbosch University