Underactuated Waypoint Tracking of a Fixed-Wing UAV

Abstract

In this paper a new method of performing waypoint tracking is shown for underactuated fixed-wing uavs. The position error can be mapped onto the desired axis using a desired rotation matrix, while the velocity error can be mapped to the desired axis using a desired angular velocity. With all errors defined along one axis, the tracking problem is easily solved using only one thruster. A velocity controller is derived which makes sure that the uav tracks a desired total velocity moving towards the next waypoint, while a sliding surface attitude controller is designed to track the desired attitude. The impact of saturation on the attitude controller is also studied where it is shown that the actuators will desaturate in finite time, through a change in the reference trajectory. Using both controllers, a solution to the problem of waypoint tracking of an underactuated uav is proposed, and simulations have been performed that support the theoretical results.

Subsumption architecture applied to flight control using composite rotations

“…The control objective can now be formalized as that of making (Ṽ , e q± , ω b d,w ) → (0, 0, 0) which can be fulfilled by using the results from [8]. This paper is concerned with the design of the desired quaternion, angular velocity and acceleration (q n,d , ω…”

“…Simulations have been performed with basis in the nonlinear dynamics and controllers from [8]. Seven uavs shall move through an urban terrain while avoiding collisions with the buildings, the ground and other uavs.…”

“…The third assumption states that the trajectories of system (A.6) must converge sufficiently fast to the origin through an integrability constraint. The sliding surface controller in [8] in closed loop with the rotational dynamics results in uniformly exponential stability of the equilibrium x 2 = 0. This means that ||x 2 || → 0 exponentially fast, thus fulfilling the third assumption.…”

“…The quaternion can be found by studying (11) resulting in (8). Equation (11) ⊤ c c which through differentiation results inV = 0.…”

A Decoupled Approach for Flight Control

“…Instead of controlling the angle of attack and sideslip directly, they can be used indirectly as part of a rotational control law that points the airspeed in a desired direction. Some preliminary results on this approach are given in Oland et al (2013) and Oland and Kristiansen (2014).…”