Development of a FBG based distributed strain sensor system for wind turbine structural health monitoring

Abstract

The development of a fiber Bragg grating (FBG) based distributed strain sensor system for real time structural health monitoring of a wind turbine rotor and its validation under a laboratory scale test setup is discussed in this paper. A 1 kW, 1.6 m diameter rotor, horizontal axis wind turbine with three instrumented blades is used in this study. The sensor system consists of strain sensors, surface mounted at various locations on the blade. At first the sensors are calibrated under static loading conditions to validate the FBG mounting and the proposed data collection techniques. Then, the capability of the sensor system coupled with the operational modal analysis (OMA) methods to capture natural frequencies and corresponding mode shapes in terms of distributed strains are validated under various non-rotating dynamic loading conditions. Finally, the sensor system is tested under rotating conditions using the wind flow from an open-jet wind tunnel, for both a baseline wind turbine and a wind turbine with a structurally modified blade. The blade was modified by attaching a lumped mass at the blade tip simulating structural damage or ice accretion. The dynamic characteristics of the baseline (healthy) blade and modified (altered) blade are compared to validate the sensor system’s ability for real time structural health monitoring of the rotor.

Feasibility study on a strain based deflection monitoring system for wind turbine blades

“…The boundary condition of a cantilever beam is given as Eq. (10). Applying the boundary condition, the solution become Eq.…”

“…The aims of measurement by FBG sensor are, for instance, to detect damage [10] or monitor structural responses such as bending loads [11][12][13].…”

Wirelessly Powered High-Temperature Strain Measuring Probe Based on Piezoresistive Nanocrystalline Diamond Layers

“…The system presented in the paper is intended to use for monitoring the stress of blade in an industrial steam turbine. The methods of structural health monitoring cover contactless tip-timing techniques using blade-tip vibrometers based on capacitive [13], magneto-resistive [14] or optical sensors [15], as well as contact techniques using fibre grating sensors [16] or mostly used strain gauges [17]. The latter method enables to monitor blade fatigue failures by studying the characteristic of flow-induced resonant vibration.…”

Comparison of epoxy and braze-welded attachment methods for FBG strain gauges

“…FBGs also boast a long-life capability and have been used extensively for strain and displacement monitoring in many industries, such as civil engineering [3][4][5], aerospace [6], as well as oil and gas [7]; most of which use epoxy based attachment methods. In previous work, brazed metal packaged FBGs [8] were used to monitor prestress in concrete [9] and for displacement measurement in spalled concrete [10].…”