Time Space Position Information Research Articles

Strap-down microelectromechanical (MEMS) sensors for high-g munition applications

Low-cost micromachined, inertial measurement sensors have steadily emerged into the commercial marketplace. Some of these sensors were evaluated through ground and flight experiments for their insertion potential into military applications like operational test and evaluation and smart munition guidance. Performance requirements for navigation and time space position information (TSPI) are fast approaching those needed, especially when integrated with a Global Positioning System (GPS). Artillery and rockets, instrumented with "automobile grade" microelectromechanical (MEMS) accelerometers and telemetry units, were recently part of a flight experiment which resulted in good success. The results of a high-g shock study suggest that some of these sensors are rugged enough to survive both low-g and high-g launch. Analyzes of the accelerometer data show good comparison to radar-based acceleration measurements and 6-degree-of-freedom trajectory simulations. Flight simulated ground experimentation with gyroscopes have also been conducted that show promise for measuring projectile pitching and yawing behavior. Recent flight experiments may also be available for comparison to ground based measurement devices. This paper presents the results of the flight and ground experimentation and describe the challenges for using these strapdown devices on rolling projectiles.

Reference Trajectories From GPS Measurements

A closed-form solution of the GPS pseudorange equations, an unaided Kalman filter, and an inertially-aided Kalman filter are used with differential GPS postprocessing to produce reference trajectories for evaluation of GPS user-equipment, for evaluation of integrated host vehicle navigation, and for accurate Time Space Position Information over large operating areas. The closed-form solution was developed in a derivation of existence conditions for solutions to GPS pseudorange equations. The derivation is included here as an Appendix. Positions calculated from the closed-form solution are used for starting and monitoring the Kalman filters, and for responding to uploads and constellation changes. Custom interface modules adapt common core modules of the aided Kalman filter to various inertial navigators.