Path-following control for fixed-wing unmanned aerial vehicles based on a virtual target

Abstract

The main contribution of this article is the proposal of a path-following method for fixed-wing unmanned aerial vehicles. This path-following method employs the multi-loop framework that consists of an outer guidance loop and an inner control loop. The guidance loop relies on the idea of tracking a virtual target. The virtual target is assumed to travel along the defined path and its speed is explicitly specified. This guidance law guarantees the asymptotic convergence to the desired path and can anticipate the transition of the flight path in advance, which reduces the command for the inner control loop. In the inner control loop, the flight control law based on dynamic surface control is derived to overcome the 'explosion of complexity' problem in the backstepping design. The numerical simulation result illustrates the effectiveness of the proposed method.

Engagement time constrained formation generation guidance following a non-manoeuvring leader

“…From equation 19, the follower speed is theoretically bounded with a maximum value of rþ1 r À Á v l for a very large error ðx d À xÞ. At the desired location, x ¼ x d , which using equation (19)…”

“…Equilibrium point. The kinematic model of the leader follower formation geometry subject to equation (1) and equation (19) can be expressed in the form of non-linear state space equation as…”

“…Secondly, a leader initial position too far away from its position at t f would require a much lower follower speed as governed by equation (19). In practice fixed wing UAVs have minimum and maximum operational speed limits and that would affect the feasible leader initial positions for a particular value of k for the proposed guidance method to work.…”

“…Modified for path following, various classical guidance laws have also found application in formation generation considering leader-follower framework. These path following methods use pursuit guidance, [15][16][17][18][19] line-of-sight guidance, 20 non-linear guidance laws based on proportional navigation 21 and trajectory shaping guidance. 22 These methods are based on guidance logics pursuing a virtual target which can potentially lead the follower to the desired relative location with respect to the leader.…”

Optimal Path-Following Guidance with Generalized Weighting Functions Based on Indirect Gauss Pseudospectral Method

“…Once the vehicle starts to track the desired path, a virtual speed related to the vehicle's speed and the separation between the vehicle and the virtual target is generated and imposed on the virtual target. By using the virtual speed and the curvature of the desired path, the states of the virtual target can be explicitly propagated along the desired path till the end of the engagement [6][7][8]. As a consequence, the position of the virtual target is always available during the entire guidance process.…”