<title>Usefulness of the fiber optic Sagnac interferometer for stability analysis of slow-speed rotation test stands</title>

Abstract

ABSTRACT Experimental results of the usefulness of the fiber-optic Sagnac interferometer for a measurement of angular position asmotion uniformity ofslow-speed rotating objects are presented. The system contains GS-13P/SR device with modified signalprocessing unit. The results of an investigation ofthis system, and their application for rotation angle and uniformity motionof object in inertial space are shown. A new slow-speed platforms generate constant angular motion (M19-03 stand made byCOBRABiD Optica) and harmonic variable motion (STW-1 stand made by AFIT) have been used as forces source. TheFourier (FFT) and wavelets (FWT) analyses have been used as mathematical description of GS-13P/SR application fortechnical diagnostic of slow-speed platforms.Keywords: fiber optic gyroscope, slow-speed velocity investigation, mechanical construction examination 1. INTRODUCTION The development of navigation, automatic control or position stabilisation systems, require an improvement of the quality ofthe angular velocity sensor used. However, studies of this sensor require a new generation of diagnostic devices allowing toobtain reliable readings, especially for lower ranges of the generated angular velocities (of the order of Earth revolutionvelocity and lower). The application ofthe fiber-optic gyroscope for testing ofsuch devices has been reported recently'. ThisGS-13P device has been successfully used for an observation ofreal momentary velocity oscillations, generated by differentslow-speed rotation test-stand available in Poland.In the present paper results of studies of a stability of rotary movement generated by M19-03 and SWT-l stands arepresented. The former one can generate constant angular velocity, whereas the latter one enables generation of harmonicvariable angular motion. To measure the real instantaneous velocity generated by these stands the modified GS-13P/SR typefibre optic gyroscope has been used. The main changes ofGS-13P/SR (Pic. 1) in comparison to the last reported' have beenmade in signal processing improvement. By an application of new lock-in amplifier SR-844 and low noise detectionpreamplifier, the system containing synchronous detection system (see Fig. 1) achieved maximal sensitivity limited byoptical head parameters.The sensor loop ofO.2-m diameter contains 500 m ofPANDA type optical fiber and high quality YORK fiber-optic polarizer.Other elements included are made using standard single-mode optical fiber. Such a solution gives decreases device cost,however does not secure long-term stability ofthe system action. It is used in different environmental conditions according toan application of special numerical software, enabling easy calculation of scale factor and other technical parameters of GS-l3P/SR system (according to PrPN-V-82002 standard). This method determines gyro and electronic constants on the base ofangular motion analysis which is performed for different rotation speed.2The GS-13P/SR system is characterised by sensitivity of 0.1 degfh, wide measuring range to 100 deg/s, transmissionbandwidth up to O kHz, and drift of 3 deg/h. Due this drift, such a system cannot be used for long-term studies. However,for short-term studies, about one minute, the drift is lower than 0.05 deg/h. In this way, the system can be used for aregistration of real parameters of the motion generated by given slow-speed stand with 0.1 degfh resolution, so twice better