Digital Homing Guidance—Stability vs Performance Tradeoffs

Digital signal processing capability can be added to a missile homing guidance system to provide a broad system decision capability against a complex threat. This processing may be on the ground or in the missile. Wherever it occurs, it introduces additional dynamics into the guidance loop which can degrade system performance. In fact, the influence of digitization is so important that it must be included at the outset in order to ensure that a guidance system design will work. One of the most significant effects is the introduction of a sample and hold in the guidance attitude loop. This paper discusses the influence of digital processing on system relative stability and performance. A variety of techniques for improving system performance are introduced and tradeoff curves are presented indicating how major subsystem parameters, such as seeker stabilization loop gain or autopilot time constant, may be specified. The results show the tradeoffs between a robust set of guidance subsystem specifications and acceptable performance when digital guidance is used.