Munitions Flight Mechanics Research

The U. S. Air Force has identified a need to develop small IMUs for tactical air launched weapon system applications. To this end, the Navigational and Control Branch (AFRL/MNGN) of the Advanced Guidance Division at Eglin AFB is currently sponsoring several efforts to develop innovative micro-electromechanical sensors (MEMS) and ultimately MEMS-based IMUs. In the near term, MEMS IMUs are expected to be developed which exhibit ! mg accelerometer errors and 50-100 deg/hr gyro errors. Although the accelerometer errors are acceptable for tactical-grade systems, the gyro errors are significantly larger than those currently associated with the mature but more costly optical-gyro (i.e., RLG and FOG) IMUs. The potentially larger gyro errors directly impact the transfer alignment requirements for a MEMS IMU equipped weapon. For example, MEMS-specific alignment procedures and algorithms may be required not only to accurately align the IMU but also to substantially calibrate the MEMS gyros. The focus of this proposed research, therefore, is to: (1) formulate high-fidelity MEMS IMU error models for near-term and far-term systems, (2) develop conventional and advanced transfer-alignment algorithms for the MEMS IMUs with special emphasis on gyro calibration, and (3) conduct simulation-based performance/cost tradeoff analyses to qualify the transfer-alignment and navigation accuracy for each IMU and candidate alignment algorithm. The results of this propose research may lead to a relaxation of the MEMS gyro accuracy specification which does not sacrifice weapon system performance.