Pusat Pengajian Kejuruteraan Aeroangkasa - Tesis

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Self-supervised learning frame work and localization using micro air vehicles for water leak detection
(2024-09-01)
Mohd Yussof, Nurfarah Anisah
Real-time detection and localization of water leakage are crucial for effective watermanagement in smart buildings. Traditional detection technologies based on static sensors frequently entail significant costs for both installation and operation. Utilizingsmall mobile robots such as Micro Air Vehicles (MAVs) provides a cost-effective and efficient for detecting objects in confined areas. Nevertheless, due to constrained processing power andlimited payload capacities, MAVs canonlydependonlightweight sensors, such as, tiny thermal sensors, which provide low image resolution and hence reduce detection distances typically within 1 𝑚. Therefore, this research presents a Self-Supervised Learning (SSL) framework, where a computer vision algorithm is developed to directly detect water leakage from thermal images, which then is used as supervised output for the training of a deep learning model by using RGB images as input. A pre-trained YOLOv4-tiny model is fine-tuned using 1080 laboratory images. Training test with 50,000 steps and 340 negative images achieves an optimal balance of accuracy, with a detection time of 0.0617 𝑠 and an average precision of 98.97%. In addition, a control strategy that combines the RGB deeplearning modeland the thermal vision algorithm is shown to allow autonomous MAVs for preliminary predictions ofwater leakage from further distances and accurately localize the leakage areas when they get closer. To validate the proposed concept, static detection tests were conducted, followed by flight tests in indoor environments. In static tests, the SSL-trained model extends the detection range from 1 𝑚 to 3 𝑚. In real-world flight tests, two scenarios are conducted: three experiments with varying initial positions and six experiments targeting different leak locations. Both static and flight tests confirm the effectiveness of the control strategy and detection algorithm in localizing water leaks in indoor environments. This research advances the sensory capabilities of MAVs equipped with RGBand thermal cameras and extends their detection range of water leakage, thereby mitigating potential damage in large or complex indoor environments.
Stability and tribological performance of dispersed graphene (gr) and aluminium nitride (aln) nanoparticles in mineral oil
(2024-08-01)
Ku Wadzer, Ku Nooryasmin
Additional nanoparticles often agglomerate and are incompatible with base fluids. With time, the mixed nanoparticles would phase-separate from the fluids, losing the benefits of aggregated nanofluids. Thus, this work examines the stability, thermal conductivity (TC), rheology, and tribology of graphene (GR) and alumnium nitride (AlN) in SUNISO 3GS refrigerant lubricant (compressor oil) and PETRONAS SYNTIUM 500 (engine oil). The study determines the best nanolubricant surfactant, the optimum concentration of GR and AlN nanoparticles in SUNISO 3GS and Engine oil 15W-40 nanolubricant, and their rheological and tribological properties. Nanolubricants' stability has been examined by visual observation and UV-vis spectrum intensity. Thermal conductivity has also been measured by changing volume percentage and surfactant presence. The highest percentage difference for TC is 22.58 in comparison with pure compressor oil. Viscosity readings at various temperatures, the ASTM 2270 standard for viscosity index measurement, and flash point were used to estimate rheological parameters. Tribological characteristics were measured using a pin-on disc tribotester to quantify wear rate according to ASTMG99. This study revealed that CTAB is the best surfactant for GR and SPAN80 is the best surfactant for AlN for both compressor oil (CO) and engine oil (EO). Next, the samples with 0.1 vol% with surfactant for both oils have the best stability and highest thermal conductivity. Furthermore, based on rheology performances, GR(0.05)-EO(CT), AlN(0.1)-EO(SP), GR(0.05)-CO(CT) and GR(0.1)-CO have the best performance. Moreover, addition of surfactant proves that it can improve the tribological performance where GR with 0.05 vol% with CTAB for both CO and EO shows the best tribological performance. Lastly, by using pin-on disc tribotester, it can be observed surfactant in nanolubricants reducing the specific wear rate (SWR) and the highest percentage difference is high as 76.37% for nanolubricant.
Classification of misfire technique using wide band oxygen sensor
(2024-09-01)
Md Sharib, Mohd Khairul Nizam
Problems with the engine often occur instability of the flame in the fuel mixture and cause it to fail to provide accurate ignition readings. In this study, a novel approach to classify the misfire techniques using wide band oxygen sensors is presented. Each signal that is given because of the failure of the fuel mixture flame should be investigated further. This research study has focused on a small single-cylinder engine with four strokes to detect the existence of abnormal conditions in engine combustion. The approach in this study began with the use of basic simulation methods through learning based on models in MATLAB through SIMULINK application version R2022b and experimental tests in the laboratory. The tested engine completed modified with the setting of input data through the Engine Control Unit (ECU) interface with Redleo Pro 9.1X software. Data was acquired with a wide band oxygen sensor and the signal was transmitted digitally by a tablet oscilloscope. The signal emitted through the oscilloscope has been analyzed and extracted by the pre processing on smooth method. The efficiency and sensitivity effects of sensory use of this wide band oxygen sensor have been observed with varying engine speed variations. The findings show abnormal combustion occurs at high-speed conditions of 4000-5000 RPM and a low Volumetric Efficiency (VE) of 2.06 % and 16.2 ignition degrees. The combination of simulation and experimental methods gives a good result by showing that lean combustion affects the signal appearance in detecting abnormal noise in the engine.
Investigation of ionospheric effects on ground based augmentation systems at low latitude region
(2024-09-01)
Rajwant Singh, Brelveenraj Kaur
Space-based technologies such as the Global Navigation Satellite Systems (GNSS) are playing an increasingly important role in aviation navigation due to the increasing demand for long-haul air travel. This encouraged airports to deploy Ground Based Augmentation System (GBAS) replacing the Instrument Landing System (ILS) which resulted in reduced delays and disruptions for travellers. Low latitudes and equatorial regions, such as Malaysia are more likely to experience ionospheric disturbances caused by solar activity and geomagnetic storms, which disturb the GNSS signals. The performance of the GNSS is subjected to risk as the integrity of the GBAS between the ground receiver and the aircraft deteriorates. This study analyse ionospheric scintillation and Total Electron Content (TEC) effects on the GBAS receivers installed at KLIA. The data collected was during solar minimum which reflected towards the GBAS in KLIA not experiencing any anomaly events that could disrupt the GPS receiver's signal during equinox months. The amplitude scintillation, S4 index values were found within (0.2 < S4< 0.5), indicating weak or negligible scintillation. The GBAS receivers consistently show of spikes of S4 data at precise times across the months, suspected due to nearby interference rather than active scintillation events. The TEC values vary from a low in the early hours of the day to a diurnal maximum between 15:00 LT and 18:00 LT before falling to a minimum in the afternoon. The TEC were particularly higher in September and March corresponding to the months of equinox. This paper investigates the ionospheric disturbance in the low latitude region and ideas for improving GBAS receiver performance for future developments.
Numerical and experimental aeroacoustic analysis of cavity at low wind speed
(2024-06-01)
Hairudin, Wan Masrurah
Wind-induced noise (aeroacoustics) in the microphone port cavity of two-way radio is a prevalent issue that significantly affects speech and audio quality, particularly in windy conditions. This thesis presents a comprehensive investigation of wind induced noise (aero-acoustic) generation in the microphone port of two-way radio through numerical and experimental analyses. A smoke visualization test was conducted in a closed wind tunnel to observe the flow structure, while a coupled direct-hybrid Computational Aero-Acoustics (CAA) method called scFLOW2Actran was employed for simulations. This method simultaneously addresses fluid and acoustics field within a single computational framework, utilizing large eddy simulation (LES) and Ffowcs William-Hawking (FW-H) acoustic analogy. The CAA investigation focuses on analyzing noise parameters such as cavity length to depth (L/D), wind speed, and wind angle orientation. Numerical results presents pressure, velocity distributions, and noise level in the near-field and far-field regions for both original and the modified microphone port geometries. The validation of the numerical results and experimental test shows a 3 dB difference at frequency of 20 Hz, confirming the feasibility of the proposed simulation method. The findings indicate that higher noise levels are observed at a cavity length to a depth of 0.7, particularly under higher wind speeds of 4.4 m/s and wind angle direction of 45°. Regarding the microphone port modifications, the result reveal that the Helmholtz resonator port with an additional aperture provides a lower reduction of 19 dB in noise level compared to others modifications. The findings also suggest that by modifying the microphone port can help reduce by weakening vortex effects. These results contribute to the understanding of wind-induced noise generation and offer valuable insights for design and acoustic engineers involved in the development of mobile telecommunication devices. The aeroacoustics analysis proves useful in devising noise reduction strategies and guiding improved microphone port design within these devices.

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