Guidance Laws for Short-Range Tactical Missiles

Introduction G laws for short-range tactical missiles have become a well-researched topic over the past 35 years with publications of analytical treatment and implementation of missile guidance going back to the 1940's. Thus, much of the guidance development available in the literature predates that which is known as modern control theory. These early concepts, now commonly referred to as classical guidance, have been used from that time to the present to command missiles during their homing phases of flight to target impact. To the extent that assumptions of comparable relative velocity and certain conditions on relative bearing between the pursuer and target were valid, the classical guidance techniques remained adequate. However, evidence is evolving which suggests that the performance of present weapon systems may be seriously degraded in engagements against targets with predicted characteristics of the 1990's and beyond and in the battlefield environments of that time frame. It has been established that the guidance laws currently in wide use may not be adequate in defeating those threats. Thus, it is projected that fundamental advances in the application of control systems theory is required to enhance the guidance effectiveness of future missile weapon systems. Additionally, missile air frame and propulsion systems also may require advances appropriate to defeat predicted targets. In particular, air defense and air-to-air weapons currently undergoing research and development utilizing classical guidance technology may be seriously hampered in the combat scenarios envisioned. In evaluating the extensive literature on guidance laws applicable to short-range missiles, the lack of a suitable survey became apparent. Although excellent reviews of related topics such as optimal control' and sensitivity methods had appeared while those fields were relatively young, the missile guidance literature was found to be highly decentralized and fragmented. This may be attributed, in part, to the fact that literature for guidance laws was usually classified for security purposes. These works were rarely published beyond internal industrial reports, and though not made public they became reference documentation for missile designers spanning a period of over 35 years. With classical techniques implemented even in today's highly sophisticated systems, the literature gave credence to a widely accepted definition of classical terminal homing and defined its extensions into the modern era. It was observed that guidance laws typically fit within the following five categories, the first three of which are the well-known classical techniques: lineof-sight (LOS), pursuit, proportional navigation guidance