Energy optimization for flying base station.

Abstract

This thesis presents ambient energy harvesting techniques to enhance endurance of a flying base station mounted on an Unmanned Aerial Vehicle (UAV) as well as to extend flight duration of the UAV mounted base station. Two techniques are presented here namely, harvesting ambient energy from flexible thin-film photovoltaic panels mounted on top of a Quadcopter fuselage. The other approach presents the use of piezoelectric generation wherein vibrations between the Quadcopter rotors and fuselage are transformed into electrical power and used to provide extra electric energy for the UAV established base station Quadcopters, also known as drones, are unmanned aerial automobiles which function without human intervention or loosely put, they are pilotless airplanes. They operate by and large in situations in which the presence of an on-board human pilot is both too risky and unnecessary hence the name UAV. Endurance for these machines is a major cause for concern in order to achieve their operational goals. Regardless of the on-board battery powering the high-power consuming motors and all equipment, the flight time is still fairly low. Either the Quadcopters need to fly to base at the end of each sortie or personnel need to follow the rotorcraft to exchange the batteries. This notably reduces overall performance and the range of operations. A lot of research is done on making Quadcopters as autonomous as possible, but to make them truly autonomous the energy problem needs to be solved.Most drones are electrically powered and there is a vital impediment on their size, weight and power hence they cannot carry enormous amount of load (i.e. payload). The energy sources are normally in the form of batteries and because of the above limitation (payload), the flight duration is commonly restrained to a few tens of minutes. The purpose of this thesis has been to deal with the energy trouble and make the Quadcopters self-sustainable over a longer time period. The proposed answer has been to use solar power to recharge the on-board batteries during flight in addition to out in the field. Unlike all known earlier attempts to use solar power for rotorcrafts, this is the first known project to modify an existing commercial quadcopter to use solar power for recharging. The results conclude that the idea of using solar power is proved to be viable for small commercially available rotorcrafts with limited or constrained available space for solar panels.The use of renewable energy sources is growing and will play an important role in the future power systems. A five parameter model of PV modules has been implemented in Simulink/Matlab. The parameters of the model are determined by an approximation method using available data sheet values. Inputs to the model include light intensity and ambient temperature. The outputs are any measurements of interests in addition to electrical power, cell temperature and voltage. Effects of varying the model parameters are demonstrated. A maximum power point tracking algorithm is used to keep the voltage at the maximum power point at all times. A battery model based on discharge curve fitting is implemented. The model is based on a fundamental battery cell which can be modified to construct many different module configurations. Power smoothing algorithms which average the input over a set time, are used to provide a power reference to the battery system.