A miniature, foldable, collision resilient quadcopter

Abstract

In the fields of surveillance, mapping and security, the use of unmanned aerial vehicles (UAVs), is becoming inevitable day by day, especially with their au-tonomous movement capabilities. The main reason for the increasing use of un- manned aerial vehicles is their ability to map and survey unknown and dangerous places such as caves without risking human life. At the same time, the ability to conduct aerial surveillance in full autonomy for public safety and health is also an important factor. Today, UAVs are used for many purposes, such as cave mapping and surveying, detection and intervention of forest fires, and inspection of outdoor and crowded areas for security purposes, often accompanied by an operator. Quadcopters are also used for missions that do not require long duration flight, as they are able to both hold position and ensure a highly stable flight. In addition to their many advantages, these UAVs are very sensitive to even the slightest impact, so their fully autonomous flight is still limited to controlled areas. Various studies are being conducted to increase the crash resistance of the quadcopters. Among these researches, there are different ideas such as protective shells and bumpers that surround the UAV and absorb the impact in case of collisions. The spherical cases that surround the UAV are usually in a mesh structure to be lightweight and not obstruct the airflow. Bumpers designed to protect the most sensitive parts of the UAV, such as the motors and propellers, are insufficient to protect the body. For these reasons, making different parts of the UAV from more flexible materials will eliminate the vulnerability of the UAV and increase its resistance to collisions. In this thesis, in order to increase the impact resistance of quadcopters and to ensure that they do not break, robots with some flexible and some rigid parts were tested and the results of these tests were evaluated in detail. During these tests, the effects of the compliance of the robot’s arms and the compliance of the bumpers protecting the propellers upon the impact were analyzed. In order to make this comparison, flexible and rigid robot bodies with dimensions as close as possible to each other, as well as rigid and flexible bumpers of similar size and structure were designed. The flexible bumper and body were produced by cutting PET sheets via a laser cutter and folding them in an origami-inspired pattern. This production method adds flexibility thanks to the thinness of the PET sheets and structural rigidity thanks to the origami-inspired folding technique. To in- crease the flexibility of the robot in the event of a collision and the stability of the motors, inserts made of TPU are inserted into the body. In addition to impact resilience, this thesis also discusses a soft sensor that can be attached to collision-resiliant drones. This sensor, made of conductive TPU, allows the robot to sense its surroundings by giving it a sense of touch. Thanks to the flexible sensor, robots can detect when a collision occurs and react accordingly. This sensor works entirely based on the flexibility of the UAV’s bumpers and senses the bending of these bumpers. Therefore, such a sensor cannot be used on rigid hulls and bumpers as they do not bend.