SITUATION: Mediadyne contracted the company to provide engineering support services for their client Lockheed Martin who was constructing a hardware-in-the-loop simulation under their Hypersonic Conventional Strike Weapon (HCSW) program with the Air Force. Part of the simulation fidelity requirements was to have software models represent actual systems of both the hypersonic vehicle and its carrier. One system that was requiring enhancement was the transfer alignment capability between the inertial navigation systems (INS) of the weapon and carrier so that the weapon INS was initialized properly before launch from the carrier.
TASK: Enhance the modeling fidelity of the transfer alignment algorithm regarding the data exchange between the weapon and carrier INS. During the transfer alignment process the carrier INS will make corrections to its navigation solution. These corrections need to be communicated to the weapon INS or the transfer alignment filter may not be able to align the weapon INS with the carrier INS.
ACTIONS: Two approaches were taken, 1) determine whether the required modeling upgrade existing from other programs, 2) develop the upgrade from first principles. Approach 1) revealed that no such algorithm existed resulting on the focus of approach 2). First reference frames were define between the earth center intertial (ECI) frame to the weapon vehicle body frame. Second small angle approximations was used to simplify the algorithm development. Third, given a mathematical formulation, a prototype of the algorithm was developed in Matlab before it was coded up in C++ of the HWIL programming language. Testing of the HWIL simulation ensured results matched those of the Matlab prototype.
RESULTS: Given specified corrections in carrier latitude, longitude, velocity and orientation, weapon vehicle body orientation corrections were able to be determined during the transfer alignment process.