Trajectory-following guidance based on a virtual target and an angle constraint

Abstract

In this paper, a new trajectory-following guidance scheme based on the combination of the virtual target concept and a missile terminal guidance law is proposed. A line-of-sight (LOS) angle constraint is derived for the unmanned aerial vehicle (UAV) to track a virtual target moving along the reference trajectory, by which the trajectory-following problem is transformed into an angle-constrained terminal guidance problem such that well-developed terminal guidance laws can be incorporated into the design of a trajectory-following guidance scheme. The nonsingular sliding mode technique is employed to control the vehicle's LOS angle to converge to its desired value and thus to tightly track the reference trajectory. In addition, the finite-time trajectory-following position error convergence of the proposed guidance scheme is presented. The significant contribution of this paper lies in the fact that a LOS angle constraint has been presented for a virtual-target-based trajectory-following scheme, greatly enhancing the flexibility of the design of the trajectory-following guidance scheme. Numerical simulations are performed to demonstrate the performance of the proposed guidance law and its superiority over existing trajectory-following guidance laws.