Extended state observer based impact angle constrained guidance law for maneuvering target interception

Abstract

In this paper, a nonsingular, essentially continuous and finite-time convergent impact angle constrained guidance law for intercepting stationary, constant speed, and maneuvering targets is developed using advanced terminal sliding mode control schemes and extended state observer. In order to achieve the specified intercept angle in finite time without singularity, the nonsingular fast terminal sliding mode control algorithm is employed to construct sliding surface. The fast terminal sliding mode control technique is used to establish the reaching law, so the system trajectory converges quickly from initial state to the switching surface in the whole reaching phase and the proposed guidance law is essentially continuous. Noticing the interception of a maneuvering target, the unknown target acceleration is estimated and compensated using extended state observer. Due to its inherent attribute of singularity-free, continuity, and faster convergence rate, no approximation is necessary in the implementation of the proposed guidance law, so better tracking accuracy of the desired intercept angle in a shorter time with a smoother guidance command can be guaranteed compared with conventional terminal sliding mode guidance law. A large number of numerical simulations are implemented to justify the effectiveness of the proposed guidance law.

Smooth Adaptive Finite Time Guidance Law with Impact Angle Constraints

“…In [33], the extended state observer based guidance law (ETSMG) is given as where 1 = 1, 2 = 2, 1 = 3, 2 = 1.5, = = 500, = 0.6, 01 = 50, 02 = 1800. The design parameters of the SANFTSMG are chosen as 1 = 30, 2 = 2.65, 1 = 60, 2 = 1.48, 1 = 4, 2 = 0.5, 3 = 118, 4 = 0.01, and = 0.68.…”

“…In order to verify the effectiveness of the proposed guidance law, as described in [32], three different target acceleration profiles are considered as given below. On the other hand, to evaluate the efficiency of the above five guidance laws, a concept of average absolute acceleration (AAA) [33] of missile is employed as where represents the total simulation steps and ( ) denotes the th step value of in simulation.…”

“…However, the expressions of the above guidance laws contain negative exponential term of the system state, which leads to the singularity problem when error being controlled becomes very small; it is almost a disaster for the attitude control system to track. To this end, the nonsingular terminal sliding mode control scheme (NTSMC) and nonsingular fast terminal sliding mode control scheme (NFTSMC) were proposed in [26][27][28] and had been successfully used to design IAGLs [29][30][31][32][33][34]. Within the above articles, the target acceleration is considered as the unknown model disturbance.…”

“…(1) Some guidance laws are noncontinuous due to the usage of the signum function [1,18,24,25,29,[31][32][33], which would pose great challenges to the system stability and deduce the control quality of the system.…”

“…(2) To determine the switching gain of the signum function, the information of the target maneuvering is required [1,18,21,22,24,26,28,29,32,33], such as the target acceleration bound, which is an unreality condition for noncooperative target. Another idea is to ignore the target acceleration [22], which is only suitable for the scenario that the maneuverability of the target (such as tanks or large ships) is far weaker than the missile.…”