Switching logic design for divert and attitude control system of exoatmospheric kill vehicle

In this paper a six degree-of-freedom (DOF) model of exoatmospheric kill vehicle (EKV) is established, which employs four divert thrusters and six attitude control nozzles to execute kinetic interception. Due to the constraint on visual field of strapdown infrared seeker, we prefer to describe the motion of ballistic warhead in EKV's body coordinates. So the relative dynamic equations between interceptor and target are derived for convenience. Then based on proportional navigation guidance (PNG) law and quasi-sliding mode method, a switching logic for divert and attitude control system (DACS) is developed. To ensure celerity and accuracy and meanwhile, avoid oscillation in the system, the method of dead zone is introduced into our logic design. In the end of study, a numerical simulation including EKV and ballistic target is made to test the performance of DACS. The simulation results are discussed and the analyses of ignition instruction and line-of-sight (LOS) angle are also given. The interception of no-maneuvering target is accurate with little consumption of propellant. But the EKV fails to hit the spiral maneuvering target unless optimal weave guidance (OWG) law is employed.