Finite-time sliding mode guidance law design with impact angle constraints

For the missile-target relative motion equations in the two-dimensional plane, a sliding mode guidance law design problem with terminal line-of-sight angle constraints in maneuvering target intercept is investigated in this paper. The attack angle constraints are transformed into line-of-sight angle constraints. A finite-time convergent linear sliding mode surface including the desired line-of-sight angle and the line-of-sight angle rate is selected. According to the target maneuvering in the system of a first-order sliding mode, the total perturbations of the target is estimated in finite time by using a non-homogeneous disturbance observer. Then guidance law is designed by using a fast power reaching law with a second-order sliding mode characteristics. Simulation results show that the missile can intercept the target with high accuracy within the desired line-of-sight angle. Meanwhile the disturbance observer can achieve the fast and high-precision estimation of the total target disturbances.