Preliminary multi-mission UAS design

Abstract

Unmanned vehicles are important when it comes to performing a desired task in a dangerous or inaccessible environment. Unmanned robots, have been successfully used for many years. More recently, a growing interest in Unmanned Aircraft Systems (UASs) has arisen. In the past few years the development of sensors, microprocessors and propulsion systems resulted in UASs that are smaller, lighter and more capable than ever before. This leads to endurance, efficiency and autonomy levels that exceed the capabilities of manned flight. A large number of successful designs have been created by several universities, commercial companies and research agencies. Due to the wide variety of applications, several configurational concepts have been developed. As a result, most UAS designs are optimized for a dedicated task. In order to perform different tasks, users need to have access to multiple UASs. This means that manufacturers and users have to maintain production and support lines for multiple UASs. The goal of this thesis was to create a preliminary design of a multi-mission UAS by using off-the-shelf systems. This UAS must be able to perform both low and high speed missions. To reach the stated goal a clear overview of all requirements had to be created first. This was followed by extensive market research in order to get an overview of the performance of current UAS designs. This market research was captured in a database. Based on the requirements in combination with the obtained database, all UAS classes and configurational options have been evaluated. The evaluation revealed that a new fixed wing electrical powered mini UAS design may be able to comply with the all UAS requirements. Based on the UAS database, weight estimation relationships for preliminary mini UAS design were derived. These relationships were used for the preliminary UAS performance and weight estimation. After investigating the technical and operational feasibility, the compliance with respect to the requirements was checked. This resulted in a new UAS design point. Subsequently, the UAS design was analyzed in more detail. Optimization of the wing was performed by using a quasi-3D optimizer. This was followed by a tail design that was based on UAS reference data and volume coefficients. The resulting wing and tail design were evaluated by investigating the wing-tail effects and the primary static \& dynamic stability derivatives. This was followed by an evaluation of the material options for the structure. During this evaluation a new manufacturing technique, 3D printing, was tested. Subsequently, the propulsion system design was performed by using a UAV Propulsion Development Kit (UPDK). This UPDK is able to estimate the performance of multiple engine-propeller combinations. Based on the evaluation of the top five combinations, a combination was selected. Finally, the additional UAS subsystems were selected. After the preliminary UAS design was completed, the effectiveness of the design was evaluated. Together with off-the-shelf systems it was possible to create a design that is able to comply with most requirements. The WER for the payload weight was found to be inaccurate. This was caused by the fact that current UASs are equipped with heavier or additional payloads. The WER for the empty weight slightly underestimated the structural weight of the UAS. Overall can be concluded that it is possible to create a preliminary mini UAS design capable of performing both low and high speed missions using off-the-shelf systems.