Research On Variable Structure Terminal Guidance Law Of Space Interception

Aerospace technology is the key technology that influences thesurvival and development of the country and nation and it’s an importantfactor to determine a country’s strategic position as well. Since the21century, China’s aerospace industry has entered a new development stage.The requirement of navigation guidance technology used in missile hasbecome increasingly tough, traditional classical and modern guidance lawhas been unable to satisfy more and more complicated interceptionrequirements. When target is maneuvering with high-speed, theperformance of traditional guidance law which only consider guidanceloop always decreases significantly, even failed to complete interception.However, there exists two inevitable problems that intercept velocitycannot be achieved and intercept window become narrow forhypervelocity target. It’s urgent to find some new and appropriate guidancelaws which can solve these problems. Via deep research on the currentdevelopment of terminal guidance law, this paper discusses its researchtrend and obtains the following research achievements:(1) This paper proposes a new guidance law which has taken intoconsideration of autopilot dynamics. Traditional guidance law is designedwith separation of control loop, therefore it does not consider the influenceof control loop to guidance precision. As with the improvement ofguidance precision requirement, guidance law without control loop’s(mainly autopilot) impact has been unable to meet the high accuracy. Inthis paper we first formulate relative motion equations taking into accountof autopilot dynamics, and then the equations are further changed into normal form by linearization and coordinate transformation. Based onLyapunov stability theory, a variable structure guidance law is presented.Considering accelerations of the target is unknown, an adaptive law isdesigned. The presented adaptive sliding mode control guidance lawcombines the advantages of variable structure control and adaptive control.Compared with traditional guidance law, its performance is betterespecially when target is maneuvering.(2) A guidance law for intercepting high-speed targets, especiallyhypersonic targets in a novel head pursuit engagement is presented. Forthere exists technical bottlenecks that cannot be overcome in a short runwhen traditional guidance law applied in hypersonic missile interception, anew technology called head pursuit is researched in this paper. This newtechnology is the most efficiency approach which can be developed in ashort time to solve hypersonic weapons. We formulate nonlinear relativemotion equations, analyze parameter conditions of head pursuit, andmaintain the intercept geometric rules to make sure that it can be used toachieve an attack with angle. Nonlinear variable structure control theory isapplied to design the guidance law. Firstly, a sliding surface when takesautopilot dynamics into consideration is designed, then adaptive controltheory is combined to derive adaptive head pursuit guidance law. Theguidance law has better performance which won’t decrease with targetmaneuver. It also has the advantage of smaller miss distance and shorterintercept time than the other head pursuit guidance laws.(3)A three dimensional visualization platform of missile interceptionis established in this paper. In order to reflect terminal guidance intuitivelyand vividly and deepen the understanding of missile interception, a threedimension missile interception platform is developed. Firstly, themathematic model and missile and target’s movement equations in thethree dimensional space are formulated. Secondly, the interceptionprogram, animation and user interface is designed. This platform revealsterminal guidance process lively and effectively and provides a good simulation platform for the follow-up research.