Guidance law of small velocity ratio interception against high-speed vehicle with impact angle constraint

Tail chase, head-on interception and head pursuit guidance methods were described by impact angle. To solve small velocity ratio intersection problem caused by developing high-speed vehicle, a kinematics model of interceptor and target was established. The effect of coplanar impact angle on approaching velocity and allowed impact area was analyzed and the velocity ratio requirement of three-dimensional intersection was studied. Based on predicted initial target velocity and moving direction, the impact angle constraint was diverted into expected line-of-sight angle via quasi parallel approach. An improved guidance law with line-of-sight angle constraint was proposed via variable structure control. The results show that the proposed guidance law achieves to guiding the line-of-sight to converge to zero as well as reaching the expected impact angle; what's more, the robustness of guidance to evaluated error of target velocity is satisfied.