A Low-Cost, Multifunction Strapdown Inertial Sensor for Tactical Applications

Thomas Pick

Abstract:	An effective inertial mid-course guidance system for tactical weapon applications only needs to operate for short flight times (1-3 minutes). The inertial gyro and accelerometer performance needed during these brief operational periods is only 1-10 degrees per hour and 0.3 - 2.0 mg (1 sigma uncertainty), respectively. This performance requirement is significantly lower than that for aircraft inertial navigators and significantly better than that for flight control applications. Studies show that a less-than-high-accuracy inertial sensor can achieve the desired performance requirements as long as the sensor demonstrates good short-term stability. If the long-term stability for a particular application is outside the desirable bounds, a rapid operational calibration/initialization could be implemented immediately preceding the tactical launch. This calibration would reduce the critical performance parameter uncertainties to the short-term stability level. Consequently, the long-term stability may be an order of magnitude less accurate than the short-term stability. Tests and analyses have shown that The Singer Company, Kearfott Division MULTISENSOR gyro-accelerometer has a long-term stability on the order of 5-100/h and 1-2 mg but it can be calibrated to better than !0/h and 300 micro-g's in 30 seconds. This dual function inertial instrument provides two axes of angular rate data and two axes of acceleration information, yet it is very small (0. 7" D x 1.7511 L). Two such instruments, with electronics, form a MULTISENSOR* Inertial Measurement Unit (MIMU). With proper initialization the MIMU should achieve Circular Error Probability (CEP) of 20 to 200 meters for tactical ranges of 5 to 100 kilometers. In this paper we describe the inertial instrument that was developed at Kearfott, the MULTISENSOR gyro-accelerometer, as well as the MIMU which is based on it, Sample performance test data are also presented. The objective for developing the MIMU was to obtain a cost-effective (cost vs. performance) inertial mid-course guidance and navigation system for short-range tactical missiles. The volume production cost target was $5,000 or less for a MIMU (with digital !iV and 6,6 outputs). The path taken was to design for low cost from inception rather than to engineer for performance and then to strive for cost goals by cost reduction methods during transition to production.
Published in:	Proceedings of the 1984 National Technical Meeting of The Institute of Navigation January 17 - 19, 1984 San Diego, CA
Pages:	1 - 10
Cite this article:	Pick, Thomas, "A Low-Cost, Multifunction Strapdown Inertial Sensor for Tactical Applications," Proceedings of the 1984 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1984, pp. 1-10.
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