As the demand for wind energy continues to grow at exponential rates, reducing operation and maintenance (OM) costs and improving reliability have become top priorities in wind turbine (WT) maintenance strategies. In addition to the development of more highly evolved WT designs intended to improve availability, the application of reliable and cost-effective condition-monitoring (CM) techniques offers an efficient approach to achieve this goal. This paper provides a general review and classification of wind turbine condition monitoring (WTCM) methods and techniques with a focus on trends and future challenges. After highlighting the relevant CM, diagnosis, and maintenance analysis, this work outlines the relationship between these concepts and related theories, and examines new trends and future challenges in the WTCM industry. Interesting insights from this research are used to point out strengths and weaknesses in today’s WTCM industry and define research priorities needed for the industry to meet the challenges in wind industry technological evolution and market growth.

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Wind Turbine Condition Monitoring: State-of-the-Art Review, New Trends, and Future Challenges

In recent few years, the antenna and sensor communities have witnessed a considerable integration of radio frequency identification (RFID) tag antennas and sensors because of the impetus provided by internet of things (IoT) and cyber-physical systems (CPS). Such types of sensor can find potential applications in structural health monitoring (SHM) because of their passive, wireless, simple, compact size, and multimodal nature, particular in large scale infrastructures during their lifecycle. The big data from these ubiquitous sensors are expected to generate a big impact for intelligent monitoring. A remarkable number of scientific papers demonstrate the possibility that objects can be remotely tracked and intelligently monitored for their physical/chemical/mechanical properties and environment conditions. Most of the work focuses on antenna design, and significant information has been generated to demonstrate feasibilities. Further information is needed to gain deep understanding of the passive RFID antenna sensor systems in order to make them reliable and practical. Nevertheless, this information is scattered over much literature. This paper is to comprehensively summarize and clearly highlight the challenges and state-of-the-art methods of passive RFID antenna sensors and systems in terms of sensing and communication from system point of view. Future trends are also discussed. The future research and development in UK are suggested as well.

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A Review of Passive RFID Tag Antenna-Based Sensors and Systems for Structural Health Monitoring Applications

This paper presents a microwave sensor using a pair of split-ring resonators (SRRs). The sensor is designed by loading a microstrip transmission line by two identical SRRs on its sides. Differential permittivity sensing is performed by loading the SRRs with dielectric samples. One transmission notch is observed for the identical loads, whereas the non-identical samples produce two split notches. The sensor’s operating principle is described through a circuit model analysis. A prototype of the designed sensor is fabricated and experimentally validated for verifying the differential sensing concept. The developed device can be used to compare or differentially characterize solid dielectric samples improving the robustness to environmental factors producing cross-sensitivity or miscalibration.

Differential Sensors Using Microstrip Lines Loaded With Two Split-Ring Resonators

The conventional resonant-type microwave microfluidic sensors made of planar resonators suffer from limited sensitivities. This is due to the existence of several distributed capacitors in their structure, where just one of them acts as a sensing element. This article proposes a very high-sensitivity microwave sensor made of a microstrip transmission line loaded with a shunt-connected series LC resonator. A large sensitivity for dielectric loadings is achieved by incorporating just one capacitor in the resonator structure. Applying sample liquids to the microfluidic channel implemented in the capacitive gap area of the sensor modifies the capacitor value. This is translated to a resonance frequency shift from which the liquid sample is characterized. The sensor performance and working principle are described through a circuit model analysis. Finally, a device prototype is fabricated, and experimental measurements using water/ethanol solutions are presented for verification of the sensing principle.

Ultrahigh-Sensitivity Microwave Sensor for Microfluidic Complex Permittivity Measurement

The processing of backscattered signals coming from RFID tags is potentially useful to detect the physical state of the tagged object. It is here shown how to design a completely passive UHF RFID sensor for strain monitoring starting from a flexible meander-line dipole whose shape factor and feed section are engineered to achieve the desired sensing resolution and dynamic range. This class of devices is low-cost, promises sub-millimeter resolution and may found interesting applications in the Structural Health Monitoring of damaged structures and vehicles as well as during extreme and adverse events.

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Passive RFID Strain-Sensor Based on Meander-Line Antennas

Wireless interrogation of circular microstrip patch antennas (CMPAs) for strain sensing is investigated by experimental measurements and computational simulations. The effect of the conductivity of the host structure on the wireless monitoring efficiency is also considered. It is shown that strain can be measured wirelessly in any desired direction using a linearly polarised horn antenna, up to a distance of 5 cm. Beyond this distance, the signal-to-noise ratio diminishes for the CMPAs employed in this study. This new contactless strain sensing technique offers significant potential for wireless structural health monitoring of civil and aerospace structures.

Wireless strain measurement using circular microstrip patch antennas

In this paper, the anisotropic conductivity efiect of quasi- isotropic carbon flber laminates on conformal load-bearing antenna structures (CLAS) is presented. The conductivity of a quasi-isotropic IM7/977-3 CFRP laminate is measured using waveguide techniques. The results show that orientation of the surface ply relative to the polarization of the incident E-fleld has a major in∞uence on the re∞ectivity. This difierence is attributed to the fact that carbon flbres oriented parallel to the E-fleld plies behave as good conductors, while ofi-axis plies present as lossy dielectric layers with a flnite conductivity. This anisotropic behavior of the ply layers is shown to have a distinctive in∞uence on the operation of both microstrip patch and slot antennas.

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The effect of ply orientation on the performance of antennas in or on carbon fiber composites

The strong diamagnetic characteristics of unidirectional carbon fiber reinforced polymer laminates

In this article, the feasibility of using a circular microstrip patch antenna to measure strain and the effects of different materials on sensitivity of the patch antenna are investigated. Also, th...

Utilising microstrip patch antenna strain sensors for structural health monitoring

In this paper the feasibility of using a circular microstrip patch antenna to detect strain has been investigated. The theoretical model shows a linear relationship between strain and the shift in the resonant frequency of the antenna. A circular patch antenna has been designed and fabricated to work at 1.5GHz. Both Finite Element Analysis (FEA) and experimental tests have been undertaken to corroborate the relationship between strain and frequency shift. The ultimate intention of this work is to configure antennas or resonators for the detection of relatively small damage zones in structures and to do so wirelessly.

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Amir Galehdar

Papers

Wireless strain measurement using circular microstrip patch antennas

The effect of ply orientation on the performance of antennas in or on carbon fiber composites

The strong diamagnetic characteristics of unidirectional carbon fiber reinforced polymer laminates

Utilising microstrip patch antenna strain sensors for structural health monitoring

Circular microstrip patch antenna strain sensor for wireless structural health monitoring