Theses and Dissertations
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Theses and Dissertations (Electrical and Electronics Engineering)
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- ItemOpen AccessDesign and Simulation of a Programmable Logic Controller for Remote Monitoring and Control of Satellite Oil and Gas Wells(2015-09-30) Ikono, Nsikan-Abasi MichaelThis study investigated development of an automatic controller for remote production restoration of oil and gas wells with a view to minimizing downtime by giving electronic logic alerts of problem areas to the system operator. The conceptual design was based on the development of a ladder logic circuitry with variable input data such as high pressure, low pressure and valves position signals sensed as "ON" or "OFF" signal levels. These input data were scanned at predetermined time intervals using the Programmable Logic Controller (PLC). The "TRIlogi 5.3" educational computer application simulator was used to simulate the workability of the ladder logic program. A remotely operated PLC system constructed with transceivers was used to demonstrate the operations by running the ladder logic program with physical model using On/Off switches as inputs and light emitting diodes (LED) as output indication. The results showed that operating the PLC logic program can achieve input variable monitoring by indicating the current statuses of the inputs with "ON" state as high pressure, "OFF" state as low pressure and "ON/OFF" as opened and closed valve positions respectively. The simulator did not require any physical connection to the target PLC, thereby offering the most effective way of testing and debugging ladder logic program prior of the hardware. Programming and debugging time were greatly reduced by making good use of the simulator feature to eliminate as many logic errors as possible before testing the program on the actual hardware. In addition, it reduced the chances of costly damage to the PLC machine due to programming errors. Moreover, it controlled the opening and closing of well production with the PLC output signals acting as feedback from the logical decision to operate end devices actuator coils with changed statuses indicated by the output LED. In conclusion, the result of the system test established the workability of remote restoration of oil and gas production using a PLC for quick decision making.
- ItemOpen AccessDevelopment of a Self-Coordinated Communication System for Scaring Birds on Rice Farms(2015-06-23) Badru, Rahmon AriyoThe study appraised techniques for communicating hazards to birds and developed a self-coordinated electronic communication system for scaring birds. It also determined the optimal placement of the bird-sensory electronic devices on the rice farms. This was with a view to solving the problem of menace of birds on rice farms. Static (e.g. scarecrow) and dynamic (e.g. drumming) methods of communicating hazards to birds through their tactile sensory cells bristle feathers, vibration sensors (Herbot's corpuscles), hearing tubes, rods and cones sensory cells were appraised in relation to their practical implementation and cost effectiveness. A prototype system was simulated by designing an infrared (IR) transmitter and receiver circuits, which were constructed using relevant combination of electronic techniques. Subsequently, an electronic IR motion detection system comprising of pyroelectric infrared sensor, Fresnel’s lens, amplifier and comparator circuits were developed and implemented. In addition, the architecture of the system was fitted with air vibration mechanisms human eye-structured and sound producing units. The overall assembly was covered with sheet of rust-free metallic sunlight reflector. The results showed that the effective coverage field and detection range for the simulated IR transmitter and receiver system were 10° and 1.5m respectively. This system was characterized with low quality siren output, faulty triggering during systems stand misalignment and inability to electronically facilitate other actuators for the effective scaring of birds. Furthermore, the self-coordinated communication system had a coverage field of 95° and a detection range of 27.4 m. The prototype of this system was observed to scare birds when the air vibration mechanism produced artificial oscillation of air molecules. The illumination produced by the human eye-structured unit coupled with the reflection of diffused sunlight rays from the body of the system disturbed the sight of the birds. Also, sound of triangular waveform signals with frequencies from 0.6 kHz to 1.5 kHz in periodic bursts of 3.0 seconds was interpreted by the birds as scare signals. In conclusion, the device was found to be suitable for the communication of hazard to birds attacking rice plants which is fundamental to improving the yield per hectare of the protected area.
- ItemOpen AccessDevelopment of a Text-Independent Speaker Identification System(2015-04-22) Fisusi, Abimbola AdeolaAccess control to confidential information and facilities is conventionally through the use of passwords, smart cards or keys that can be stolen or forgotten. In this work, a software-based access control system that identifies users by the unique features in their voices, which cannot be easily breached, was developed with a view to overcome the limitations of conventional access control methods. The implementation of the system involved two phases - the training and testing phases. During the training phase, speech samples were collected from seven male and five female speakers by recording their voices with a microphone connected to a computer system. Speaker's unique features were extracted from the speech samples in form of Mel-Frequency Cepstrum Coefficients (MFCCs) which estimated the unique shape of the spectral envelope of each user. The extracted MFCCs features were used to build speaker models in form of codebooks for the speakers using the Vector Quantization (VQ) approach. The speaker models created were stored in a database. During the testing phase, another set of speech samples were collected from the same set of speakers of the training phase. MFCC features were extracted from each of the testing speech samples and compared with the codebooks created during the training phase. For each testing speech sample, the speaker whose codebook gave the lowest average distortion was identified as the true speaker. Codebooks of different sizes ranging from 16 to 256 were used to perform the identification task. In the same vein, the performance of the system as a text-dependent system was also evaluated using the same words for both training and testing phases. The performance of the text-independent speaker identification system was evaluated by comparing the speakers' testing phase MFCCs with their training phase codebooks. The results showed that the identification rate of the text-independent speaker identification system increased with increase in codebook size. "The identification rate of the system was 57.14% when 16-vector codebooks were used as speaker models. It was 71.43% and 85.71% for 32-vector and 64-vector codebooks respectively. The speaker identification system was able to achieve 100% identification rate at codebook sizes of 128 and 256. The average distortions of speakers from testing speech samples were found to decrease with increase in codebook size. The 128-vector codebooks are preferred over 256-vector codebooks because the time required to perform the identification task is shorter for 128-vector codebooks although both give 100% identification rate. 1n conclusion, the developed text-independent speaker identification system could distinguish between speakers correctly and provide security for confidential information and facilities better than conventional methods if the codebook size used for the identification task is large enough.
- ItemOpen AccessRainfall Attenuation on Earth-Satellite Microwave Link in a Tropical Environment(Obafemi Awolowo University, 1987) Odunewu, Paul Adekunle; Ajayi, G.O.Rainfall is a major impairment to radiowave propagation at centimeters and millimetre wavebands, moreso in the tropics because of the intensity, frequency of occurrence and presence of large drops in tropical rainfall. In order to determine the vertical extent of rain (rain height) in the tropics, the characteristics of 0°C isotherm height have been studied using radiosonde data collected at three stations in Nigeria for three years at each station. One year rain rate data collected at Ile-Ife using an electronic rapid response rainguage have been analysed in order to obtain the cumulative rain rate distribution. The existing rainfall attenuation prediction models have been examined. Three attenuation models viz: CCIR, Global and SAM, have been utilized to predict slant path attenuation at Ile-Ife from the one-year rain rate distribution. Cumulative distributions of predicted attenuation were obtained for different frequencies, earth station's elevation angles and polarizations. Attenuation distributions from the three models have been compared. The result obtained shows that 0°C isotherm height during rainy season decreases from the southern to the northern part of Nigeria. A mean 0°C isotherm height of 4. 8 km for the rainy season has been obtained for Nigeria. The rain intensity exceeded for 0.01% year at Ile-Ife was obtained to be 87 mm/h. The differences in the attenuation values predicted by the three remodels vary for different percentages of time, frequencies, elevation angle and polarizations. The results obtained in this work could be used for providing necessary fade margin in satellite link budgets in Nigeria and other similar tropical environment.
- ItemOpen AccessDevelopment of a Synchronous Data Transmission System.(Obafemi Awolowo University, 1986) Agomo, Uchenna Udochukwu; Kehinde, L. O.The development of a 2 - channel synchronous data transmission system is presented. The system is capable of accepting at the input two separate analog voltage signals that have zero to 1 kHz frequency range and amplitude not greater than 2.5 volts. The two analog voltage signals are multiplexed at the input of the-system and converted to corresponding digital representations. These digital representations are then transmitted by means of digital gates from the transmitting section serially and with transmission clock frequency of 6.6 MHz, through cable wire to a remote receiving section, where the received digital representations are re-converted to analog voltage signals and demultiplexed to produce at the output, two separate analog voltage signals plus noise. The noise level does not exceed 5% of the signal level when filtered and leaves analog voltage signals with the same characteristics as those at the input of the system. The designed system is simple and can be used for laboratory demonstration on synchronous data transmission system. It may be useful as a communication medium for data exchange between two data processing terminals. The system may be used to transmit voltage signals from a central storage facility to a remote destination. In such circumstance the signals may be those derived from research results, medical findings and student/staff records. A computer base may then be set up and made accessible to users.