Adaptive reaching law based three-dimensional finite-time guidance law against maneuvering targets with input saturation

Considering the problem of a missile intercepting a maneuvering target with impact angles constraints, three-dimensional engagement dynamics are established in this paper. Then two finite-time guidance laws are proposed based on the coupled dynamics. The first finite-time anti-saturation guidance law is designed using the finite-time observer. Besides, this guidance law uses the exponential reaching law, which requires the upper bounds of observation errors. Therefore, to solve the defects existing in the exponential reaching law, a novel reaching law is proposed, which can accelerate the convergence rate of sliding mode surfaces and weaken the chattering phenomenon. Moreover, it can be widely used in the design of sliding mode controllers. Next, based on the novel reaching law, the second finite-time guidance law is given without the knowledge of the upper bounds of observation errors. Numerical simulations are introduced to demonstrate the effectiveness and superiority of the designed composite guidance laws in theory.