Slab deflection measurement technique based on fiber optic gyro

ABSTRACT The development and successful application of fiber optic gyro (FOG) supply the potential possibility for performingaccurate slab deflection measurement. In this research, an algorithm method is put forward for calculating slab deflectionbased on the output of FOG and an in-door model test was conducted. Experiment reveals that FOG is applicable forstructure deflection measurement. Its measurement accuracy will satisfy the requirement of engineering if high-accuracyFOG is adopted.Keywords: fiber optic gyro, slab deflection, measurement accuracy, algorithm, model test 1. INTRODUCTION Deflection is. one of the most important parameters that are used to evaluate the behavior of structure. It has become thenecessary content ofmany monitoring programs. However, at present normal measurement techniques are not applicable forsome special engineering, for example the slab deflection measurement of concrete-faced rockfill dams. The main problemexists in the presence of reservoir water that curbs the application of normal measurement method. To overcome this kind ofproblem, researchers have studied for many years on the technique of horizontal inclinometer. But its application does notresult in reliable and accurate measurement. Now 64 electrolevel meters are being embedded in the slab of 1 86m-highTianshengqiao concrete-faced rockfill dam to evaluate slab deflection. However, their effectiveness still needs the test ofpractice. Therefore a kind of high-accuracy and practical measurement meter should be exploited to satisfy the demand ofengineering monitoring. Nowadays fiber optic sensor is developing rapidly and has many advantages, such as high accuracy,low cost and electromagnetic resistance.Among various types of fiber optic sensors, fiber optic gyro (FOG) has become the most sophisticated. It provides rotationdetection based on the principle of "Sagnac effect". Since the initial proposal of FOGs in 1976, many aspects have beenstudied. The Interferometer FOG (I-FOG) has passed the turning point toward the practical application stage. I-FOGs havealready been used in the traditional application fields of the gyro, such as aircraft navigation, rocket control, and shipnavigation. Intermediate grade I-FOGs have already been used in the navigation system for the newest aircraft, the Boeing777. FOGs have significant advantages over traditional spinning mass gyros, such as having a short warming-up time, beinglight weight, maintenance free and reliable, and having a wide dynamic range, large bandwidth, low power consumption andlow cost. These features have created new applications, including car navigation, antenna camera stabilizer, crane control,unmanned vehicle control, etc.