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Collision Resilient UAV
Fall 2019 - Spring 2020
Overview
In Fall 2019, I started working as an undergraduate research assistant at the High Performance Robotics Laboratory with Dr. Mark Mueller, where I gained first-hand experience related to Unmanned Aerial Vehicles (UAVs). I worked on designing a tensegrity structure for collision resistance in a UAV. I researched different materials, performed stress and data analysis, and came up with a new design that could absorb energy from the collision without altering any of the UAV’s structural components. After many iterations, the design not only achieved one of the highest velocities a collision resistance UAV can survive but also cut the structure’s weight by half. The paper I co-authored about this work was successfully accepted for publication by the International Conference on Intelligent Robots and Systems (IROS 2020). This project not only expanded my knowledge on how to properly set up functional experiments but also the importance of iteration during the design process since there is always room for improvement.
About the Tensegrity Structure
To protect the vehicle from collisions at high speed, we have decided to use a icosahedron tensegrity, which is a structure mainly based on a system of rigid bodies that experience compression under a tension network. For this project, I mainly focused on the designing, manufacturing, and experiments of the icosahedron tensegrity structure aerial vehicle.
Tensegrity Aerial Vehicle
Design Approach & Experiments
The end caps are one of the most important parts of the design since every time there is a collision most of the energy is absorbed by the end of the rods. I started by finding the correct snap fit between the end-cap and the rod as well as the minimum hole required to insert the nut without damaging the structure.
End-cap tolerances
The final end cap design has a total height of 10 mm long, it has four 2.30 mm gaps to hold the strings, and there is a pre-made 1.5 mm diameter hole for the M2 screws to be threaded through as shown below.
End-cap
End-cap design holding the strings
End-cap assembly
The structure design was optimized by using shorter end-caps to avoid breaking from collision and the manufacturing process changed from using alignment brackets to a new 3D printed structure that helps to hold the structure together. The key to manufacture the tensegrity structure is the following 3D-printed support. The support consists on four separable parts that hold the six rods parallel to each other. Zip ties and heavy duty tape is required to attach the rods to the support. Once the tensegrity shape is completely ready and the strings are tighten, it is possible to take out the support from the inside by removing all the ties and tape and separating each one of the support’s pieces without affecting the tensegrity structure.
3D printed support
Old alignment bracket
Finalized tensegrity structure with 3D printed support
In addition to working with the manufacturing part of the robot, I constructed experiments that showed that the structure could survive more than 5 meters height free-fall drops and I also worked with the motor characterization in order to map the PWM to make the motor rotate in both directions.
Payload to replicate drone's weight for testing purposes
3.3 m drop test
Final Result
The tensegrity structured aerial vehicle is collision resilient and can achieve collisions at a speed of up to 6.5 m/s. It also includes an autonomous reorientation controller that helps the vehicle to resume operations after collision.
Publication
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