Adaptive Terminal Guidance for Hypervelocity Impact in Specified Direction

Abstract

The problem of guiding a hypersonic gliding vehicle in the terminal phase to a target location is considered. In addition to the constraints on its final position coordinates, the vehicle must also impact the target from a specified direction with very high precision. The proposed 3-dimensional guidance laws take simple proportional forms. The analysis establishes that with appropriately selected guidance parameters the 3-dimensional guided trajectory will satisfy these impact requirements. We provide the conditions for the initial on-line selection of the guidance law parameters for the given impact direction requirement. The vehicle dynamics are explicitly taken into account in the realization of guidance commands. To ensure high accuracy in the impact angle conditions in an operational environment, we develop closed-loop nonlinear adaptation laws for the guidance parameters. We present the complete guidance logic and associated analysis. Simulation results are provided to demonstrate the effectiveness and accuracy of the proposed terminal guidance approach. I. Introduction Recent interests in developing on-demand global-reach payload delivery capability have brought to the forefront a number of underlying technological challenges. Such operations will involve responsive launch, autonomous entry flight, and precision terminal maneuvers. In certain scenarios the mission requirements call for the payload to impact the target location from a specific direction with supersonic speed. One example is to impact the target in a direction perpendicular to the tangent plane of the terrain at the target. The terminal guidance system will be responsible for directing the vehicle to the target and achieving the desired impact direction. The impact precision requirements under the scenarios considered are very high and stringent. For instance, the required Circular Error Probable (CEP) of the impact distance is just 3-meter. 1 The errors of the impact angles are desired to be within 0.5 deg. The very high speeds throughout the terminal phase only make it considerably more difficult to achieve these levels of precision. Yet cost considerations dictate that the terminal guidance algorithm should be relatively simple and computationally tractable for real-time operations. While a number of guidance methods can guide the vehicle to the target, not many address the unique need for impact from a specific direction. One method that can is the so-called “dive-line” guidance approach in Ref. 2. In this method one or more lines intersecting the Earth are established. The final dive-line intersects the target, and its direction can be set to the desired direction. The vehicle’s velocity vector is