Innovative sensor networks for massive distributed thermal measurements in space applications under different environmental testing conditions

Optical fiber has seen significant development in the technical fields where it has been used in the last years. In the first place, obviously, for the Internet and, more broadly, to improve communication efficiency; but, more recently, for medicinal, structural, or lighting engineering applications. Furthermore, many optical solutions are beginning to be researched in the aerospace sector. The use of optical fiber, in particular, is strongly related to the employment of FBG type optical sensors, which may be particularly suitable for specific measurements of relevant physical parameters to be performed on specimens with typical aeronautical and/ or space employment. More specifically, the performance of several FBG sensors for temperature measurement in vacuum for validation tests of space products has been examined during this work. Unlike typical thermocouples, the adoption of this new type of sensor can provide substantial benefits, beginning with a significant gain in terms of the size of the fiber, which ensures a minimum disturbance on thermal data. Furthermore, if supplied with a suitable coating (in polyimide), the optical fiber may guarantee a very high operating temperature range, which is extensively compatible with the high-temperature range existent in space. The measurements were divided into two independent phases. First, a preliminary test was performed in the laboratory using a climatic chamber to evaluate several sensor network integration methodologies on the specimens and select the most effective one for the vacuum test. The test demonstrated that a simple adhesive bonding of the fiber to the specimens ensures a precise temperature measurement under vacuum and stable conditions. The following vacuum test program confirmed that FBGs could be used as temperature sensors even at very high temperatures. The good results of this test encourage us to consider FBG strategic for space applications and, particularly, for thermal characterizations, thanks to the high number of available sensors, combined with the minimal cable's size. However, further studies are required in cryogenic cases to validate the entire range of extreme temperatures that characterize the space environment

Thermomechanical calibration of FBG sensors for aerospace applications

Optical fibers have found widespread use in engineering, from communication to sensors. Among them, Fiber Bragg Gratings are allowed to detect several parameters. Scope of this work is to assess their performances as temperature and mechanical strain sensors for aerospace: in this regard, an experimental calibration is discussed. Then, alternative approaches are tested in order to distinguish thermal from mechanical contributes. This is first addressed by using a hybrid system of digital and optical sensors, and then then with a fully optical system. Both the presented solutions reached the scope. A concept of a third, innovative approach, is also described

A genetic-based prognostic method for aerospace electromechanical actuators

Prior awareness of impending failures of primary flight command electromechanical actuators (EMAs) utilizing prognostic algorithms can be extremely useful. Indeed, early detection of the degradation pattern might signal the need to replace the servomechanism before the failure manifests itself. Furthermore, such algorithms frequently use a model-based approach based on a direct comparison of the real (High Fidelity) and monitor (Low Fidelity) systems to discover fault characteristics via optimization methods. The monitor model enables the gathering of accurate and exact data while requiring a minimal amount of processing. This work describes a novel simplified monitor model that accurately reproduces the dynamic response of a typical aerospace EMA. The task of fault detection and identification is carried out by comparing the output signal of the reference system (the high fidelity model) with that acquired from the monitor model. The Genetic Algorithm is then used to optimize the matching between the two signals by iteratively modifying the fault parameters, getting the global minimum of a quadratic error function. Once this is found, the optimization parameters are connected with the assumed progressive failures to assess the system's health. The high-fidelity reference model examined in this study is previously conceptualized, developed, implemented in MATLAB-Simulink and finally experimentally confirmed

Study of FBG-based optical sensors for thermal measurements in aerospace applications

Optical fibers have revolutionized several technological sectors in recent decades, above all that of communication, and have also found many applications in the medical, lighting engineering, and infrastructural fields. In the aerospace field, many studies investigated the adoption of fiber optics considering the planned transition from fly-by-wire to fly-by-light flight controls. A significant feature of optical fiber is its ability to be used not only as a transmission medium but also as a basis for fiber-embedded sensors; one of the most prominent types is based on Bragg gratings (FBGs). FBGs can replace several traditional sensors, providing measures of temperature, vibrations, and mechanical deformation. Optical sensors provide many advantages over traditional, electrical-based sensors, including EMI insensitivity, ease of multiplexing on a single line, resilience to harsh environments, very compact sizes and global weight saving. Furthermore, punctual knowledge of the temperature field is essential to perform the thermal compensation of the optical sensors used for strain measurements. In this work, the authors analyzed the performance of thermal sensors based on FBGs to verify their stability, accuracy, and sensitivity to operating conditions. Two different methods of FBGs surface application have been considered (gluing with pre-tensioning vs. non-tensioned bonding). The results were then compared to those acquired using typical temperature sensors to determine the relationship between the observed temperature and the Bragg wavelength variation (i.e. the proportionality coefficient Kt). The effects on the proportionality coefficient Kt, arising from fiber pre-tensioning and thermal expansion of the structural support, were then evaluated by comparing the results obtained with the two bonding approaches

Analysis of navigation pattern in the sport of rowing

The effect of weather and environmental conditions on sports has been extensively studied over the last few years (Pezzoli et al., 2010). Based upon the studies of Lobozewicz (1981) and of Kay and Vamplew (2002), Pezzoli and Cristofori (2008) have studied the impact of some specific environmental parameters over different sports using a particular impact index divided into five classes. This analysis clearly shows that most of the outdoor sport activities are strongly influenced by the variation of meteorological parameters. However the impact of meteorological conditions on outdoor sport activities has not yet been extensively studied. The aim of this research is to show that an accurate assessment of wind and wave parameters enables decisive improvements in both training and race strategy planning. Furthermore this analysis provide a very innovative working method for the applied sport research. The work has been based on in-situ measurements of both environmental and performance parameters (wind direction, wind velocity, boat speed and stroke rate) made over different classes and in different race conditions during the 2009 FISA World Championship (Poznan, Poland). In particular a detailed environmental analysis was performed by measuring the wind direction, the wind speed and by evaluating the significant wave height and the wave peak period for each class during the semi-final phase and the final phase. It should be noted that, since wind is a key parameter affecting not only the boat speed but also the race strategy, the assessment of the wind velocity and of the wind direction has been made in connection with the boat movement. The comparison between coupled wind-wave data, boat speed and stroke rate evidently demonstrates that only crews that managed the adaption to changing in the environmental conditions from semi-final to final phase of the race, were able to get better results. References Kay, J., & Vamplew, W. (2002) Weather beaten: sport in the British climate. London: Ed. Mainstream Publishing. Lobozewicz, T. (1981) Meteorology in sport. Frankfurt: Ed. Sportverlag. Pezzoli, A,, Moncalero, M., Boscolo, A., Cristofori, E., Giacometto, F., Gastaldi, S., & Vercelli, G. (2010) The meteo-hydrological analysis and the sport performance: which are the connections? The case of the XXI Winter Olympic Games, Vancouver 2010, Journal of Sports Medicine and Physical Fitness, 50: 19-20. Pezzoli, A., & Cristofori, E. (2008) Analisi, previsioni e misure meteorologiche applicate agli sport equestri, in: 10th Congress "New findings in equine practices, Druento: Centro Internazionale del Cavallo Ed., p.38-4

VLTI/PIONIER images the Achernar disk swell

Context. The mechanism of disk formation around fast-rotating Be stars is not well understood. In particular, it is not clear which mechanisms operate, in addition to fast rotation, to produce the observed variable ejection of matter. The star Achernar is a privileged laboratory to probe these additional mechanisms because it is close, presents B-Be phase variations on timescales ranging from 6 yr to 15 yr, a companion star was discovered around it, and probably presents a polar wind or jet. Aims. Despite all these previous studies, the disk around Achernar was never directly imaged. Therefore we seek to produce an image of the photosphere and close environment of the star. Methods. We used infrared long-baseline interferometry with the PIONIER/VLTI instrument to produce reconstructed images of the photosphere and close environment of the star over four years of observations. To study the disk formation, we compared the observations and reconstructed images to previously computed models of both the stellar photosphere alone (normal B phase) and the star presenting a circumstellar disk (Be phase). Results. The observations taken in 2011 and 2012, during the quiescent phase of Achernar, do not exhibit a disk at the detection limit of the instrument. In 2014, on the other hand, a disk was already formed and our reconstructed image reveals an extended H-band continuum excess flux. Our results from interferometric imaging are also supported by several H-alpha line profiles showing that Achernar started an emission-line phase sometime in the beginning of 2013. The analysis of our reconstructed images shows that the 2014 near-IR flux extends to 1.7 - 2.3 equatorial radii. Our model-independent size estimation of the H-band continuum contribution is compatible with the presence of a circumstellar disk, which is in good agreement with predictions from Be-disk models

High gear ratio mechanical transmissions for actuators: Simplified models for efficiency under opposing and aiding loads

Planetary gear drives are widely employed in electrical and hydraulic actuation systems, to adapt a high speed, low torque motor to a low speed, high torque user, within strict weight and volume constraints. During the early design phases of these devices, accurate yet simple simulation models are required to evaluate the performance of a given configuration of the device. Similar models are also useful within diagnostic and health monitoring analyses of existing machines, as a discrepancy between the actual behaviour of the physical system and that predicted by its digital twin may be the effect of a damage. This work compares different models available in literature for the efficiency of high gear ratio mechanical transmissions; the models are applied to multiple arrangements common for planetary drives, and the results in form of an efficiency map for the transmissions are compared and discussed. The simulations provide different levels of detail, and require different levels of knowledge about the specific architecture of the system. All of them are able to deal with dry friction; additionally, the different behaviour of the transmission under the effect loads aligned in the same direction of speed or in the opposite one is accounted for

Nanostructured tic layer is highly suitable surface for adhesion, proliferation and spreading of cells

Cell culture is usually performed in 2D polymer surfaces; however, several studies are conducted with the aim to screen functional coating molecules to find substrates more suitable for cell adhesion and proliferation. The aim of this manuscript is to compare the cell adhesion and cytoskeleton organization of different cell types on different surfaces. Human primary fibroblasts, chondrocytes and osteoblasts isolated from patients undergoing surgery were seeded on polystyrene, poly-d-lysine-coated glass and titanium carbide slides and left to grow for several days. Then their cytoskeleton was analyzed, both by staining cells with phalloidin, which highlights actin fibers, and using Atomic Force Microscopy. We also monitored the production of Fibroblast Growth Factor-2, Bone Morphogenetic Protein-2 and Osteocalcin, using ELISA, and we highlighted production of Collagen type I in fibroblasts and osteoblasts and Collagen type II in chondrocytes by immunofluorescences. Fibroblasts, chondrocytes and osteoblasts showed both an improved proliferative activity and a good adhesion ability when cultured on titanium carbide slides, compared to polystyrene and poly-d-lysine-coated glass. In conclusion, we propose titanium carbide as a suitable surface to cultivate cells such as fibroblasts, chondrocytes and osteoblasts, allowing the preservation of their differentiated state and good adhesion properties

Study of Packaging and Installation of FBG Sensors for Monitoring of Aircraft Systems

Next generation aircraft systems will feature an ever increasing complexity. In this context, advanced health monitoring strategies will be required to ensure a high level of operations safety as well as a good reliability. Hence, Prognostics and Health Management (PHM) is emerging as an enabling discipline for future advanced aircraft design and operations, with a particular application to Flight Control System (FCS) monitoring. One of the most critical issues for real-time Fault Detection and Identification (FDI) of aircraft FCS is the availability of actuator load measurements. The aerodynamic load on flight control actuators has a significant influence on their dynamic response, and can easily hide the effect of incipient failure precursors. For this reason, real-time monitoring FDI algorithms relying on the comparison between the actual system response and that of a digital twin require either a measure or an estimation of aerodynamic loads. Usually, this quantity is not monitored by a dedicated sensor, since it is not required as a feedback signal by most control logics. A dedicated load sensor for PHM with traditional technologies is not easily feasible: for example, a load cell would be mechanically connected in series with the actuator, adding a potential single failure point and affecting the overall system safety; the use of strain gages on the structure is less accurate, and requires several sensors with individual wiring and complex signal conditioning circuitry. Optical strain sensors based on Fiber Bragg Gratings (FBG) allow indirect load measurement combined with real-time structural monitoring, combining an acceptable increase in complexity and costs with a high robustness. In this preliminary study, we installed an FBG monitoring system on a UAV to assess the feasibility of such technology. Measures of structure deflection were correlated to actuator position and IMU data, to estimate aerodynamic loads

Analysis of navigation pattern in the sport of rowing

The effect of weather and environmental conditions on sports has been extensively studied over the last few years (Pezzoli et al., 2010). Based upon the studies of Lobozewicz (1981) and of Kay and Vamplew (2002), Pezzoli and Cristofori (2008) have studied the impact of some specific environmental parameters over different sports using a particular impact index divided into five classes. This analysis clearly shows that most of the outdoor sport activities are strongly influenced by the variation of meteorological parameters. However the impact of meteorological conditions on outdoor sport activities has not yet been extensively studied. The aim of this research is to show that an accurate assessment of wind and wave parameters enables decisive improvements in both training and race strategy planning. Furthermore this analysis provide a very innovative working method for the applied sport research. The work has been based on in-situ measurements of both environmental and performance parameters (wind direction, wind velocity, boat speed and stroke rate) made over different classes and in different race conditions during the 2009 FISA World Championship (Poznan, Poland). In particular a detailed environmental analysis was performed by measuring the wind direction, the wind speed and by evaluating the significant wave height and the wave peak period for each class during the semi-final phase and the final phase. It should be noted that, since wind is a key parameter affecting not only the boat speed but also the race strategy, the assessment of the wind velocity and of the wind direction has been made in connection with the boat movement. The comparison between coupled wind-wave data, boat speed and stroke rate evidently demonstrates that only crews that managed the adaption to changing in the environmental conditions from semi-final to final phase of the race, were able to get better results. References Kay, J., & Vamplew, W. (2002) Weather beaten: sport in the British climate. London: Ed. Mainstream Publishing. Lobozewicz, T. (1981) Meteorology in sport. Frankfurt: Ed. Sportverlag. Pezzoli, A,, Moncalero, M., Boscolo, A., Cristofori, E., Giacometto, F., Gastaldi, S., & Vercelli, G. (2010) The meteo-hydrological analysis and the sport performance: which are the connections? The case of the XXI Winter Olympic Games, Vancouver 2010, Journal of Sports Medicine and Physical Fitness, 50: 19-20. Pezzoli, A., & Cristofori, E. (2008) Analisi, previsioni e misure meteorologiche applicate agli sport equestri, in: 10th Congress “New findings in equine practices, Druento: Centro Internazionale del Cavallo Ed., p.38-43