A. G. Solov and A. P. Kantrowitz

Peer Reviewed

Abstract: The requirement for a sensitive failure detection and isolation (FDI) capability for the space shuttle orbiter IMU system has been an important aspect of the development of the IMU for some time. In an earlier ION paper, a method for performing these functions for soft instrument failures in a 2-IMU environment was presented, along with preliminary results. Additional studies of the performance capabilities of the technique for realistic shuttle trajectories followed and were published. The current paper addresses two areas which these earlier efforts showed to be potentially fruitful in improving the performance of the 2-IMU soft FDI approach. It is shown that improvement of the sensitivity of the skewed IMU FDI mechanization can be accomplished by (1) more accurate knowledge of cluster to cluster attitude and (2) appropriate selection of isolation geometry. Reduction of relative azimuth uncertainty due to gyro-compassing is shown to be possible by the use of the high accuracy gimbal angle readout devices to be used on the Space Shuttle IMU. Accelerometer FDI is shown in this paper to be significantly improved by the reduction of this error source. Additional improvement of the FDI capability is shown to be possible by careful selection of isolation geometry. It is shown that testing of the error vector against geometric spaces of various shapes changes the isolation probability, and that a very simply mechanized space has the attendant advantage of providing very high true isolation probabilities. Finally, data collected from Monte Carlo simulations of the FDI mechanization, applied to a Space Shuttle boost trajectory, are presented to demonstrate typical improvements which can be obtained through the application of these techniques.
Published in: NAVIGATION: Journal of the Institute of Navigation, Volume 22, Number 1
Pages: 51 - 58
Cite this article: Solov, A. G., Kantrowitz, A. P., "RECENT RESULTS IN FAILURE DETECTION AND ISOLATION FOR THE SPACE SHUTTLE IMU", NAVIGATION: Journal of The Institute of Navigation, Vol. 22, No. 1, Spring 1975, pp. 51-58.
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