The EMPF is currently investigating an issue to improve the reliability of synchro-based guidance systems used in Navy surface ships by upgrading the synchro signal amplifier assembly with state-of-the market solid state technology. Both navigation and radar detection utilize ranged information (speed, distance, elevation, and azimuth) for course corrections and for determining the location of a possible hostile threat. EMPF engineers recently evaluated synchro signal systems aboard LPD7 class ships (Figures 1-1 and 1-2), which enabled the engineers to see first hand the end application impacting the war fighter and the importance of improving the reliability of the system through manufacturing technology upgrades.
Synchro is a generic term for an electromechanical mechanism consisting of a configuration of transducer elements with a shaft and a gear set that provides angle and position measurements. The synchro coordinates gear-to-gear information (synchro signal) with an amplifier stage to a set of panels that allows for control and corrections. Approximately five hundred twenty eight (528) synchro boxes are installed in one hundred twenty three (123) ships across twelve classes of naval vessels. It is the ship's gyrocompass that provides the synchro-based control signal to perform the required system responses.

Going Solid State with Open Architecture
The issues regarding the current configuration include frequency of repairs and alignments necessary due to mechanical contact with the intended repair item. Elimination of the mechanical interdependency would resolve most of the repair issues including access, required skill-level, parts availability, and the resultant down-time.

NASA's Marshall Space Flight Center has developed a digital circuit which produces a signal for precise control of the position and rate of rotation for single or multiple shafts. That is, a circuit that emulates the synchro signal. There are commercially available converter products (such as synchro to digital, and synchro to resolver circuits) but they are more suited to less critical applications.

The use of a solid state version of the synchro amplifier assembly introduces labor, cost, and mean time between failure improvements worthy of pursuit. The EMPF is working with a select group of vendors to produce a solid state version of the synchro amplifier assembly. The features will include an open architecture approach to allow for future revision, partial upgrades, ease of repair, and discrete device replacement. The units will reduce the mechanical nature of the signal interfacing, thus preventing current interdependent-type repairs to the associated gears.

Some of the issues to be handled in the new design include thermal dissipation and an increase of MTBF (mean time between failures) to 80,000 hours. Failure prediction can be accompanied by built-in-test, with shutdown and thermal overload recovery decisions applicable. The need for cost-effective, low-risk solutions exists. Decreasing the number of items to be repaired leads to a decrease in subsequent time invested in the repair, and to significant cost savings.

Navy Benefit
The utilization of solid state modular assemblies will reduce the repair and maintenance costs of the fielded signal amplifier assemblies. Currently, a repair to the synchro signal amplifier requires a costly and elaborate disassembly process, followed by repair and realignment of the associated gear assembly. The solid state version eliminates the input gears. The time to repair a synchro amplifier will also be reduced through increased MTBF, open architecture, increased availability of parts (reduction of obsolescence), elimination of interdependent repairs, and an overall less complex repair of the assembly.

References
1) "Azimuth and Elevation" article, unknown author, Techtarget.com and WhatIs.com, July 15, 2002. http://whatis.techtarget.com/definition/0,289893,sid9_gci838808,00.html

2) "Azimuth" article, unknown author, Heavens-above GmbH, c.2002.
http://esa.heavens-above.com/esa/azimuth.asp