194 research outputs found

    Use of optical fibres for multi-parameter monitoring in electrical AC machines

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    This paper describes a new approach to multi-parameter monitoring for electrical AC machines. It is demonstrated that speed, torque and temperature can be measured using optical fibres incorporating sensors in the form of fibre Bragg gratings (FBGs) distributed around the machine. One fibre can incorporate several FBGs and hence provide several measurements. Experimental results showing speed, torque, direction of rotation, stator housing vibration and temperature measured using the FBG method are presented and validated against measurements obtained from conventional sensors. The results show that the optical fibre based approach allows multiple parameters to be monitored accurately and simultaneously with only a fraction of the usual monitoring equipment required. Another advantage of the proposed method is the EMI immunity naturally provided by optical solutions. The presented measurement technique can also offer a new alternative approach to sensorless control

    Coaxial Cable Sensors Based on Fabry-Perot Interferometers and Their Applications in Distributed Sensing

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    Aging civic infrastructures in the world has put tremendous pressure in their maintenances because potential failure of the large size civil structures will be catastrophic. Structure health monitoring (SHM) has been proven effective to prevent these failures, and distributed sensing technologies are preferred in SHM as they are effective to provide comprehensive evaluation of the structures. Fiber optic sensors are well developed in the past two decades for distributed sensing, but the lack of robustness and the limited deformability of silica make them not suitable for heavy duty and large deformation applications, which is very common in SHM. To address the above limitation of optical fiber sensors, we change the sensing platform from optical fibers to coaxial cable. Inspired by optical FPI, we created two reflectors on a coaxial cable to form a coaxial cable Fabry-Perot interferometer (CCFPI). The reflectors are commonly made by drilling half way holes or crimp on the cable, which introduce impedance discontinuity and hence partial reflection of EM wave in the cable. The two reflectors can produce interference patterns with multiple resonant frequencies which can be tracked to indicate changes in physical parameters such as temperature and strain. To realize distributed sensing, multiple reflectors are implemented along a coaxial cable, where every two consecutive reflectors will form a low finesse CCFPI. A specific signal process technique is used to reconstruct each individual CCFPI interferogram from the complex frequency domain signal. As examples of the distributed sensing capability of the coaxial cable platform, distributed torsion sensing and 3D beam shape estimation system are demonstrated in this thesis. By modifying the cable material and structure, we can achieve other special function for CC-FPI sensors. By fabricating the cable with ceramics as dielectric material and implanting built in reflectors, a high temperature CC-FPI sensor is developed and tested. Another example is a magnetic field sensor made by filling a cavity in a semi-rigid cable with ferrofluid. When external magnetic field change, the property of the ferrofluid will also change, resulting in spectrum shift of the FPI. The coaxial cable FPI sensors have many potentials to measure different physical parameters in distributed sensing form, which makes it a very good sensing platform for long distance and distributed sensing in harsh environment and heavy duty applications

    Fiber Optic Strain Sensor for Planetary Gear Diagnostics

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    This paper presents a new sensing approach for helicopter damage detection in the planetary stage of a helicopter transmission based on a fiber optic strain sensor array. Complete helicopter transmission damage detection has proven itself a difficult task due to the complex geometry of the planetary reduction stage. The crowded and complex nature of the gearbox interior does not allow for attachment of sensors within the rotating frame. Hence, traditional vibration-based diagnostics are instead based on measurements from externally mounted sensors, typically accelerometers, fixed to the gearbox exterior. However, this type of sensor is susceptible to a number of external disturbances that can corrupt the data, leading to false positives or missed detection of potentially catastrophic faults. Fiber optic strain sensors represent an appealing alternative to the accelerometer. Their small size and multiplexibility allows for potentially greater sensing resolution and accuracy, as well as redundancy, when employed as an array of sensors. The work presented in this paper is focused on the detection of gear damage in the planetary stage of a helicopter transmission using a fiber optic strain sensor band. The sensor band includes an array of 13 strain sensors, and is mounted on the ring gear of a Bell Helicopter OH-58C transmission. Data collected from the sensor array is compared to accelerometer data, and the damage detection results are presente

    Diagnosis of broken bar fault in three-phase induction motors using fibre bragg grating strain sensors assisted by an algorithm

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    Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáIn this study, we developed an algorithm for identifying failures caused by broken bars in the rotors of three-phase induction motors through the analysis of their dynamic deformation using fibre optic Bragg gratings (FBGs) as sensing elements. The analysis of dynamic deformation enables the detection and diagnosis of various mechanical faults, such as misalignment, imbalance, bearing failures, and mechanical looseness. Furthermore, it allows for the identification of electrical faults, such as fractures or cracks in the rotor rings or bars To measure the dynamic deformation, we employed FBG-based sensors known for their key features, including high multiplexing capability, electromagnetic radiation immunity, and long-distance operation. Experimental tests were conducted on a small-scale induction motor (3 HP) to validate the method and explore its applicability to medium and large-scale machines. The motor was powered by two different supply sources: the utility power grid and a controled power sources, under load conditions of 75% and 100% of the rated load. During the tests, we used a rotor without any bar defects and subsequently a rotor with a broken bar. The presence of a broken bar was successfully identified under both load conditions and across all two power supply sources. The fault caused by the broken bar in the rotor was detected in two frequency regions obtained from the three sets of experiments. The first region was centred around the mechanical rotational frequency of the rotor, while the second region was approximately twice the electrical frequency of the power supply. The system demonstrated high sensitivity with a good signal-to-noise ratio and showcased advantages over conventional methods and sensors commonly used for identifying broken bar faults in induction motors.Neste estudo, desenvolvemos um algoritmo para identificar falhas em barras quebradas no rotor de motores de indução trifásicos por meio da análise da deformação dinâmica do estator usando grades de Bragg em fibras ópticas (FBGs) com assitência de um algoritmo. Essa análise possibilita a detecção e o diagnóstico de várias falhas mecânicas, como desalinhamento, desbalanceamento e folga mecânica. Além disso, permite a identificação de falhas elétricas, como fraturas ou rachaduras nos anéis ou barras do rotor. Para medir a deformação dinâmica, empregamos sensores baseados em FBG conhecidos por suas principais características, incluindo alta capacidade de multiplexação, imunidade à radiação eletromagnética e operação a longa distância. Testes experimentais foram conduzidos em um motor de indução em pequena escala (3 HP) para validar o método e explorar sua aplicabilidade em máquinas de médio e grande porte. O motor foi alimentado por duas fontes de alimentação diferentes: a rede elétrica de utilidade pública e por uma fonte controlada, sob condições de carga de 75% e 100% da carga nominal. Durante os testes, utilizamos um rotor sem defeitos no rotor e, posteriormente, um rotor com uma barra quebrada. A presença da barra quebrada foi identificada com sucesso em ambas as condições de carga e em todas as duas fontes de alimentação. A barra quebrada no rotor foi detectada em duas regiões de frequência obtidas a partir dos três conjuntos de experimentos. A primeira região estava centrada em torno da frequência rotacional mecânica do rotor, enquanto a segunda região era aproximadamente o dobro da frequência elétrica da fonte de alimentação. O sistema demonstrou alta sensibilidade com uma boa relação sinal-ruído e apresentou vantagens sobre os métodos convencionais e sensores comumente usados para identificar falhas em barras quebradas em motores de indução

    Smart Manufacturing in Rolling Process Based on Thermal Safety Monitoring by Fiber Optics Sensors Equipping Mill Bearings

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    The steel rolling process is critical for safety and maintenance because of loading and thermal operating conditions. Machinery condition monitoring (MCM) increases the system’s safety, preventing the risk of fire, failure, and rupture. Equipping the mill bearings with sensors allows monitoring of the system in service and controls the heating of mill components. Fiber optic sensors detect loading condition, vibration, and irregular heating. In several systems, access to machinery is rather limited. Therefore, this paper preliminarily investigates how fiber optics can be effectively embedded within the mill cage to set up a smart manufacturing system. The fiber Bragg gratings (FBG) technology allows embedding sensors inside the pins of backup bearings and performing some prognosis and diagnosis activities. The study starts from the rolling mill layout and defines its accessibility, considering some real industrial cases. Testing of an FBG sensor prototype checks thermal monitoring capability inside a closed cavity, obtained on the surface of either the fixed pin of the backup bearing or the stator surrounding the outer ring. Results encourage the development of the whole prototype of the MCM system to be tested on a real mill cage in full operation
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