Browsing by Author "Carrola, Pedro Miguel Costa"
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- In-flight thrust measuring system using onboard force transducerPublication . Carrola, Pedro Miguel Costa; Gamboa, Pedro VieiraThe present work focused on the implementation and validation of an in-flight thrust measuring system using onboard instrumentation. This system was integrated and tested onboard the 01¬harapo UAV, from the Aerospace Sciences Department of University of Beira Interior, resulting from the need to have a fully equipped and instrumented flying test bed to assess and validate variable span wings prototypes using morphing technologies. This system comprises a force transducer (load cell) and a compatible signal conditioner which filters and amplifies the load cell signal. An infra-red temperature sensor was also added to the system in order to correct the thrust readings for temperature effects. The load cell signal conditioner and temperature sen¬sor communicate with the UAV flight management unit which works as data acquisition system. The in-flight parameters regarding propeller thrust and load cell temperature can be real-time monitored. The load cell was completely characterised in terms of its calibration curves both within and without the compensated range. Then, an assessment was conducted to quantify the UAV transmission shaft friction magnitude. Thereafter, with both the load cell calibration curves and with the friction compensation equation, the final in-flight thrust equations were found and implemented into the UAV flight management unit. At this stage, the entire in-flight thrust measuring system was characterized in terms of its performance, that is, in terms of its non-repeatability, non-linearity, hysteresis and creep. Regarding the system validation process, in-flight and wind tunnel tests were performed. These tests were conducted for different air¬speeds and different throttle settings in order to obtain thrust values for different propeller advance ratios. An uncertainty analysis was also carried out with the aim of attaining the accu¬racy and precision level of the various results obtained. ln general, for lower throttle settings (below 35% of the full throttle), the system seems to have low sensitive to measure low thrust magnitudes. Nevertheless, and despite all the factors that had a negative effect on the mea¬suring system accuracy, for throttle settings above 35% the in-flight thrust values showed a satisfactory agreement with the corresponding wind tunnel ones. For future system iterations, a few enhancements were proposed as well.