Browsing by Author "Rajendran, Parvathy"

Now showing 1 - 5 of 5
  • Thumbnail Image
    ItemOpen Access
    Development of design methodology for a small solar-powered unmanned aerial vehicle
    (Hindawi Publishing Corporation, 2018-03-27) Rajendran, Parvathy; Smith, Howard
    Existing mathematical design models for small solar-powered electric unmanned aerial vehicles (UAVs) only focus on mass, performance, and aerodynamic analyses. Presently, UAV designs have low endurance. The current study aims to improve the shortcomings of existing UAV design models. Three new design aspects (i.e., electric propulsion, sensitivity, and trend analysis), three improved design properties (i.e., mass, aerodynamics, and mission profile), and a design feature (i.e., solar irradiance) are incorporated to enhance the existing small solar UAV design model. A design validation experiment established that the use of the proposed mathematical design model may at least improve power consumption-to-take-off mass ratio by 25% than that of previously designed UAVs. UAVs powered by solar (solar and battery) and nonsolar (battery-only) energy were also compared, showing that nonsolar UAVs can generally carry more payloads at a particular time and place than solar UAVs with sufficient endurance requirement. The investigation also identified that the payload results in the highest effect on the maximum take-off weight, followed by the battery, structure, and propulsion weight with the three new design aspects (i.e., electric propulsion, sensitivity, and trend analysis) for sizing consideration to optimize UAV designs.
  • Thumbnail Image
    ItemOpen Access
    Experimental analysis of small solar ummanned aerial vehicle to predict aerodynamic performance
    (National Institute for Aerospace Research - INCAS, 2020-12-31) Rajendran, Parvathy; Smith, Howard
    Various studies have been done in recent years on unmanned solar-powered aircraft for non-stop flight at a specified location or area. However, if a solar-powered unmanned aerial vehicle (UAV)can achieve a non-stop flight around the world, it may lead to the possibility of a pseudolite (i.e., pseudo-satellite) operation. These solar UAVs capable of operating as a satellite enable sustainable aviationthat provides cheaper communication accessibility. Recently, we have developed a mathematical model for solar UAVs that was followed by the fabrication of a solar UAV model. Both the mathematical design model and the prototype model have been published. Thus, this work aims to determine the actual flight performance characteristics of the fabricated solar UAV. In this work, the bench and flight tests of the prototype solar and non-solar UAV model were compared in terms of aerodynamic characteristics and performance. These characteristics are determined using the flight test data and then compared with simulation data using a mathematical design model published earlier. Both accelerated and un-accelerated methods have been applied to predict the polar drag curve, and a distinct band of data obtained for both UAV prototypes. The predicted zero-lift drag coefficients were similar to the theoretical prediction in these UAVs
  • Thumbnail Image
    ItemOpen Access
    Modelling of solar irradiance and daylight duration for solar-powered UAV sizing
    (Multi-Science Publishing, 2016-02-02) Rajendran, Parvathy; Smith, Howard
    Solar energy from the sun is the largest available renewable energy that enhances the endurance of a solar powered unmanned aerial vehicle. However, harnessing this solar power is a great challenge. This is due to having solar module system’s power output efficiency of only about 15–30%. However, a solar powered unmanned aerial vehicle has the potential to outperform a battery only operated unmanned aerial vehicle, especially when task being a pseudo satellite which requires long operating hours. The atmospheric conditions and geological locations undoubtedly the main cause for poor performance of these solar modules. In spite of its prolific improvement in solar cell efficiency over the years, the overall solar module system barely converts half of sun’s power into electricity. Therefore, this situation makes the current system unattractive to be widely used for energy harvesting. Recent attention has been focused not only on type of solar cells but on its positioning system. However, there were lack of understanding and research on the solar irradiance intensity and daylight duration’s effect on the power output. Therefore, a comprehensive model was developed to study on how the sun movement affects the solar module system’s performance. This simulation model has identified the daylight duration is more important in comparison to the available solar irradiance. Moreover, the higher the solar irradiance and daylight duration, the solar module system gives the most power output. The daylight duration also depends on the latitude where the higher the latitude gets, the longer the daylight duration. Besides, the longitudinal coordinates and elevation have minor effect on the daylight duration estimation. In other words, in summer, the northern hemisphere has more advantage compared to the southern hemisphere locations and vice versa.
  • Thumbnail Image
    ItemOpen Access
    Sensitivity analysis of design parameters of a small solar-powered electric unmanned aerial vehicle
    (Taylor's University, Malaysia, 2018-12-31) Rajendran, Parvathy; Smith, Howard
    The design, fabrication, and operation costs of a solar-powered unmanned aerial vehicle (SUAV) only comprise a small fraction of the various aspects of satellite systems. Given the easy redeployment of SUAVs with a newly enhanced payload, many researchers have become interested in studying the potential of SUAVs as pseudo-satellites. However, research on the capability of a small SUAV to achieve year-round global perpetual operation remains in its infancy. The endurance of small SUAVs may be further improved by reducing system weight and power consumption. Therefore, sensitivity analyses are performed to determine the effects of payload, propulsion’s weight to power ratio, and solar module’s weight to area ratio on the weight and power consumption of a small SUAV. The outcome of this investigation is vital to avoid unnecessary investment on product development that may not significantly improve the performance and capabilities of SUAVs. The payload exerts the greatest effect on the maximum take-off weight of a SUAV, followed by the battery, structure, solar module, and propulsion weight. The weight to area ratio of the solar module should be prioritized in technological advancements to promote the endurance of SUAVs. In addition, small SUAVs will considerably benefit from improvements in the weight to power ratio of the propulsion.
  • Thumbnail Image
    ItemOpen Access
    Single cell Li-Ion polymer battery charge and discharge characterizations for application on solar-powered unmanned aerial vehicle
    (Trans Tech Publications, 2017-01-31) Rajendran, Parvathy; Mazlan, Nurul Musfirah; Smith, Howard
    Solar-powered UAV is an alternative way to achieve high endurance and long range UAV flight. However, solar irradiance is not always available during the flight. Thus, secondary power source which is electrical batteries will improve the performance of solar-powered UAV when solar irradiance is not available. Therefore, bench test for LiPo battery is conducted in this paper for the design of solar-powered UAV power system. The impact of operating temperature at various charging and discharging rate on the duration to full charge and discharge and capacity level of a single LiPo battery were assessed. The solar module installed in solar-powered UAV developed by Aircraft Design Group, Cranfield University has to be designed to charge the battery pack at a nominal or maximum rate of 0.129 C and 0.155 C correspondingly. The solar module requires roughly 5.73 hours on nominal charging rate on 30 °C operating temperature to fully charge capacity level instead of 5.54 hours theoretical predicted. The battery pack will then discharge at cruise flight roughly about 0.071 C to a maximum of 1.685 C if required. If the battery pack is not charged, during cruise flight the battery capacity will deplete completely at about 6.51 hours for the same operating temperature, in contrast to the 6.48 hours based on the theoretical prediction. In addition, the usage of LiPo batteries for operation at high altitudes and/or extreme temperatures without an additional heating or cooling system for these battery packs is not favorable. Thus, it is best to charge at low charging rate and high operating temperature to store and utilize the most capacity from this battery.