Research On Guidance And Control Law With On-off Control Input For Near Space Interceptor

Near space hypersonic vehicle has been developed rapidly for fast-moving and continuous-maneuvering.It can be destroyed by the accurately guided interceptor via hit-to-kill technology.This requires the precision guidance technique with finite time convergence.In particular,the thruster on the interceptor can only output an on-off type thrust with a lag.Moreover,the target seeker on the interceptor can only measure the line-of-sight(LOS)angle.In this dissertation,the guidance and control methods are designed based on finite-time control theory and observer for near space interceptor.Considering that the thrust produced by the thrusters is approximately a constant and the final time of the guidance process is finite,two guidance laws with finite time are designed based on finite-time control theory.One is the bang-bang type guidance law.The sufficient condition for finite time convergence is rigorously proved in both the planar and three-dimensional environments.According to the sufficient condition and the guidance period,a guidance law with hysteresis-band switching is proposed.Simulation results show that the LOS angular rate converges to the origin in finite time,and the condition for finite time convergence is testified.The proposed guidance law can avoid the zigzag motion of the LOS angular rate and reduce the switching frequency of thruster.The other is the finite-time convergent guidance law and the PWPF modulator with variable open threshold.Theoretical analysis and simulation results show that the proposed guidance laws are robust against target maneuvers,the LOS angular rate converges to the origin more rapidly and the working time of thruster is increased.In consideration of the influence of missile body dynamic delay on guidance accuracy,finite-time guidance laws on account of thruster dynamics are designed.First,the dynamics of thruster is viewed as a first-order lag with on-off working style and is integrated with the target-interceptor engagement dynamics to design guidance law.Bang-bang type nonsingular sliding mode guidance law is proposed,and its sufficient condition for finite time convergence is strictly proved.The nonsingular sliding mode guidance law with hysteresis-band switching is designed based on the minimum working time and the sufficient condition for finite time convergence.They are integrated to yield a composite guidance law.Simulation results show that the proposed guidance law can effectively compensate for the dynamics.Secondly,the guidance model without LOS angular acceleration rate is established.Bang-bang type linear sliding mode guidance law is proposed,and its condition for finite time convergence is proved.Correspondingly,the linear sliding mode guidance law with hysteresis-band switching and composite guidance law are given.Simulation results show that the proposed guidance laws have better guidance performance in the presence of measurement noise.Thirdly,the guidance model considering the second-order lag of the thruster is established.The sliding mode guidance law with hysteresis-band switching can guarantee that the LOS angular rate converge to a neighborhood of origin in finite time.Simulation results show that the proposed guidance law has better guidance accuracy than the guidance law without considering the dynamics or only considering the first-order dynamics.Only with the LOS angle measured by the target seeker as input and define the item of target acceleration as an augmented variable,two extended state observers are designed to estimate the LOS angular rate and the target acceleration without any model assumption on the target maneuver.One is the linear extended state observer based on the guidance model considering the first-order lag.The nonsingular sliding mode guidance laws with bang-bang type and hysteresis-band switching are implemented based on the estimations.The other is the high gain extended state observer.The estimations are used to realize the finite-time convergent guidance law and the PWPF modulator.Simulation results show that the designed observers can effectively estimate the LOS angular rate and target acceleration,and the proposed guidance laws using the estimations can satisfy the interception accuracy requirements.Considering of the drift of interceptor mass center,two robust attitude control laws are presented under control variable constraint.Moreover,the coupling problem of thrusters in roll and yaw channels is solved.One is the bang-bang linear sliding mode control law which is used in the decoupled three-channel attitude control model.The sufficient condition for finite time convergence is strictly proved.The chattering is eliminated by the boundary layer,and a three-channel attitude control law with dead zone is given.The simulation results have testified the condition for finite time convergence,and the allocation scheme of thrusters meets the requirements.The other is the nonlinear attitude control law based on the back-stepping technique.Moreover,the estimation of the nonlinear disturbance observer is used in the control law to improve the robustness.PWM converts the control law to the working time of the thruster.The simulation results have verified the performance of disturbance observer and composite control law.Furthermore,PWM has good modulation effect.Considering that attitude control and guidance control are closely related,the guidance and control design of interceptor are studied aiming at two typical targets in near space.In the background of anti X-51 A,the nonlinear control law based on disturbance observer is employed in the attitude control,and the composite guidance law considering the first-order dynamics based on linear extended state observer is adopted in the guidance control.In the background of anti HTV-2,bang-bang attitude control law is employed in the attitude control,and the finite-time convergent guidance law and the PWPF modulator based on extended high gain observer are adopted in the guidance control.Monte Carlo test has considered the thrust misalignments of the thruster,the drift of the interceptor mass center and the measurements noise of the target seeker.The results show that the proposed guidance and control design can intercept the target via hit-to-kill technology.