An improved nonsingular fast terminal sliding mode guidance law with impact angle constraints

In the paper, an improved nonsingular fast terminal sliding mode (INFTSM) guidance law with impact angle constraints is proposed. The guidance law, which employs a double power reaching law and an attractor with negative exponential factor, has a fast speed no matter far from the sliding surface or approach. For the maneuvering targets, extended state observer is designed through which the unknown lateral acceleration of target can be estimated and contributed to make compensation for the motion. Compared with other nonsingular guidance law, the proposed INFTSM guidance law not only has a better performance in impact angle and miss distance, but also show advantage in shorter time and higher accuracy. Numerical simulation results are presented to illustrate the proposed guidance law.