Anti-aircraft Artillery (AAA) Federation
Article by: Bob Kent  (kent@eglin.af.mil) Introduction The 96th Communications Group, Modeling and Simulation Support Flight (96 CG/SCTO) is responsible for assessing and introducing emerging modeling and simulation (M&S) capabilities to its customers for munitions and C4I systems testing. To this end, a Development Test Cell (DTC) has been established in the Freeman Computer Sciences Center at Eglin AFB to support the migration to High Level Architecture (HLA). The goal of the HLA is to establish a common technical framework to facilitate the interoperability of models and simulations, C4I systems, and test range assets and to promote the reuse of M&S components. This DTC provides the resources for development and testing of HLA applications at Eglin AFB. HLA Compliance A 10 Sep 96 memorandum signed by the Under Secretary of Defense for Acquisition and Technology mandates that all DoD simulation programs use the HLA and set a timetable for review of simulations and develop migration plans. To facilitate adherence to these requirements, Eglin began developing the HLA DTC in August 1997. By November, the equipment was procured, people were trained, and an initial HLA demo was operational. The initial efforts were aimed at understanding the requirements of HLA and assessing the impact of making a legacy model set HLA compliant. Legacy Model Set This legacy model set consists of high fidelity real-time threat surface-to-air missile (SAM) and anti-aircraft artillery (AAA) flyout models, which provide miss distance as a measure of effectiveness in support of Electronic Combat testing at several DoD test facilities. The facilities include the Air Force Flight Test Center (AFFTC), the Air Armament Center (AAC), the Air Force Electronic Warfare Evaluation Simulator (AFEWES), and the Naval Air Warfare Center, Weapons Division (NAWC/WD) at China Lake, CA. These flyout models were developed under an AF/TE Range Improvement Initiative funded in 1994. The Modeling and Simulation Support Flight keep them under strict configuration control in the Flyout Model Information Center (FMIC).   The information used to develop the models was approved by the Defense Intelligence Agency (DIA). Validation has been completed on many of the models by the Simulation Validation (SIMVAL) office of the National Air Intelligence Center (NAIC). The remaining models will be validated when funding is available. To date, the FMIC contains fourteen missile simulations, two gun simulations, and off-line executives used for post mission data reduction. All of the software developed for the FMIC adheres to sound software-engineering methods, including comprehensive documentation. Since the models are used to support testing at multiple facilities, they use a set of interface standards known as the Standard Interface for Missile Simulations (SIMS) and the Standard Interface for Gun Simulations (SIGS) which address model taxonomy, model interface, coordinate systems, and sign conventions. The Federation Development Process The AAA Federation was developed in four steps using the SAM Federation as a blueprint. Since we were building the AAA Federation from the SAM Federation, and wanted to be current with the latest RTI, our first step was to convert the SAM Federation from utilizing RTI version 1.0 release 3, to utilizing RTI version 1.3 release 4. Although there were a minimal number of lines of code to change, there were a number of new concepts to embrace such as federates "looping" to join the federation, federates "ticking" the RTI to "enableTimeConstrained" and "enableTimeRegulation". In addition, other concepts included allowing federates to specify (via the "RTI_MESSAGE_VERSION" environment variable) the RTI executive to be utilized, changing RTI time to a C++ class named "RTIfedTime", and "checksumming" RTI initialization data (RID). During this step, it was noted that the wall-clock execution speed of the simulation did not significantly increase using the RTI.rid file distributed with RTI version 1.3 release 4. Investigation into modification of the RTI.rid for this purpose is planned, with utilization of the Defense Modeling and Simulation Office (DMSO) RTI RID Editor.   In the third step, the AAA Federation was developed from the SAM Federation by implementing the AAA FOM, the AAA Model federate was developed from the SAM Model federate by implementing the AAA Model federate SOM, and the AAA Model legacy code was substituted for the SAM Model legacy code. There is a correlation between the AAA Model and the SAM Model. The AAA Model is composed of firing doctrine, a fire control director, a gun servo, and the projectile simulation. Correspondingly, the SAM Model is composed of a pre-launch computer, missile guidance, missile autopilot, and missile airframe. By combining the components into one Model module, and using the previously mentioned interface standards to communicate between the Model federate and the Model module, the Model federate can be reused for a suite of models.   In the fourth and final step, the AAA Federation remote observer/plot federate was developed from the SAM Federation remote observer/plot federate, and displays AAA PCA data. The AAA Federation executes across a local area network (LAN) on both Windows NT and SUN workstations, as did the SAM Federation. The AAA Model Federate was certified HLA Compliant by DMSO on 02 December 1998. The migration of the legacy model set is not yet complete. Since the legacy model set is well documented and good software engineering practices were used, we are in the process of verifying that the legacy AAA models operate as expected within the AAA Model Federate. Point of Contact For general information about the AAA Federation contact Bob Kent, (850) 882-2693, e-mail: kent@eglin.af.mil.
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