Development of a multi-rotor VTOL UAV : mechanical design of a 3D printed compliant surface

• Main Author: Tay, Mervyn Kai Yuen
• Other Authors: Ng Bing Feng
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/76429
• Institution: Nanyang Technological University

While majority of morphing wing compliant surfaces constitutes a mixture of either metals, alloys, smart materials and some additive manufactured components, this project aims at investigating the feasibility of a fully integrated 3D printed VTOL UAV compliant surface, capable of internal actuation. This report started by reviewing the applications of various morphing technology onto different conventional wing surfaces. Subsequently, the different trailing edge morphing configurations, consisting of both direct actuation and smart materials shape changes were highlighted and the concept of the FishBAC morphing actuation was progressively selected for integration into the project. The diverse applications of 3D printing techniques for different UAV configurations, along with the topological arrangements designed via Solidworks, and the testing and fabrication of selected 3D printing techniques were being elaborated and discussed in detail. Multi-material 3D printing PolyJet technology was adopted for the fabrication of the compliant surface due to its ability to manufacture intricate details of high resolution, as well as the ability to integrate both rigid and flexible surfaces in a single print. A shore hardness of 50A was ultimately chosen for the flexible trailing edge after material experimentation. Internal electrical components encompassed a Raspberry Pi microcontroller and a pair of TowerPro SG90 servo-motors were selected for initiating the actuation of the compliant surface. The tendons of the compliant surface constitutes a pair of monofilament nylon strings responsible for sustaining the required deflection. Putty, an open sourced terminal emulator tool was used in conjunction with Python script for the programming of the Raspberry Pi and its servo-motors. Optimisation techniques included the Mean Square Error (MSE) approach for the OpenCV image recognition for an automated displacement of the servo-motors. Future works included the implementation of embedded electronics with 3D printing, the integration of Shape Memory Alloy (SMA) and Voronoi Diagrams for structural optimisation for an increase in the actuation capability, reduction in weight and improvement in overall flight efficiency.