TRUNAVTM: A LOW-COST GUIDANCE/NAVIGATION UNIT INTEGRATING A SAASM-BASED GPS AND MEMS IMU IN A DEEPLY COUPLED MECHANIZATION

摘要

This paper addresses the need within the Projectile andrnPrecision Guided Munitions marketplace for a highprecisionrnguidance and navigation unit with a size,rnweight, power and cost suitable for ogive and eventuallyrnfusewell integration. Rather than being driven byrnseparate GPS and IMU performance specifications, thernTRUNAVTM navigation performance should bernconsidered at the system level by enhancing navigationrnoutput of the combined GPS/IMU system. In order tornoptimize performance when subjected to jamming and/orrnhigh dynamics, the TRUNAVTM includes ultra-tightlyrn(also known as deeply) coupled GPS/InertialrnMeasurement Unit (IMU) integration as well as hardwarernappliques. As part of the size, weight, power, and costrnreduction, the IMU digital signal processing, guidancernfunction, control function and fuzing function will berngradually re-hosted on the GPS receiver processor(s),rnthereby reducing the overall number of boards.rnIEC is the world’s first company to house both advancedrnGPS receiver technology and MEMS inertial sensorrntechnology under one roof. The TRUNAVTM includesrnIEC’s GRAM/SAASM GPS receiver that is Wide ArearnGPS Enhancement (WAGE) capable, IEC’srnMicroSCIRAS (Micromachined Silicon Coriolis InertialrnRate and Acceleration Sensor) MEMS inertialrntechnology, together with navigation, guidance, autopilot,rnfuzing, and built-in-test (BIT) functionality, into a singlernproduct. The TRUNAVTM design includes a "customerrnarea" to accommodate customer needs for a specificrnplatform integration. TRUNAVTM deep couplingrnimplementation utilizes the federated approach in which arnbank of fast Kalman filters process the I and Q correlatorrnoutputs and generate measurements for a larger, slowerrnfilter to compute a navigation solution, calibrate IMUrnerrors, and close the tracking loops. Between filterrnupdates, the IMU, corrected for errors estimated by thernnavigation filter, is driving the NCOs.rnA high-fidelity simulation including IEC's tracking andrnnavigation software was developed. In addition to arncomplete GPS environment and a motion generator, thernsimulation includes a user-selectable IMU error model, asrnwell as IEC's tracking and navigation software for bothrnthe standard tracking loops and deep couplingrnmechanizations. This, coupled with the ability to simulaterna user-selected J/S, make for a powerful design andrnanalysis tool. The simulation was baselined by comparingrnsimulated tracking loop performance versus actualrnreceiver performance under various jamming andrndynamics scenarios. It was then utilized to develop therndeep coupling mechanization and determine thernperformance improvement as a function of dynamics,rnIMU quality and J/S environment. TRUNAVTMrnarchitecture will be described and simulation results willrnbe presented.