Progress Blog 3 - Why we're doing this

10/16/2021

"Sometimes, it's difficult to think the senior projects we work on will ever matter. Most of them never will... and are regulated to closets at a university or, even worse, a file saved in a computer long lost. 

But some lucky few get the chance to do something that shows to you just how important the project you work on matters, not just to you, but to those who need it most. This week I got that chance to get that experience, working with our partners in the industry and with our partners in police to participate in a event with a happy ending.

On Wednesday, October 6th around mid afternoon, a 3 year old child followed a dog into the dense forest of Magnolia, Texas. After a 12 hour waiting period, search and rescue efforts began to hunt for the missing child. A manhunt was called and a search and rescue began, led by police from Magnolia County. Starting Friday, they began accepting volunteers in the robotics sector, including from unmanned pilots. I, alongside one of our partner police departments, signed up for shifts.

I got the chance to fly Saturday morning, waking up at 6AM to drive for an 1hr30min to the drone command center. There, we got the chance to work with FTA-UAS, who had setup as the primary command center and was coordinating the unmanned side of the search and rescue. I flew with them for about 4-5 hours, until, thankfully, the kid was picked up by a local 5 miles away. The foliage, the forest, all of the nooks and crannies, were extremely challenging terrain by all standards. It was almost impossible for any known robot to fly through that foliage - we were ordered to fly 150ft AGL, and even then we almost hit trees. We weren't the ones who found the kid, but the work we did in mapping the terrain, generating target data, and the experience all of us gained in robotics, shows us just how important these projects are and why they matter.

I'll get the chance to thank FTA-UAS someday, when they visit UH sometime next semester. But we learned an extremely valuable lesson in how search/rescue ops were created, what features they know matter, and most importantly why what we're doing matters. And that's an important note to take for the future.

We'll have a more formal progress blog in the future, as well as a video of our actions. But for now... Here are the actual team updates."

-- Bernard Li, CEO, Limited Technologies


Progress Update

The team has been gathering data for potential materials to use for the drone frame. The data includes densities, tensile yield strengths, hardnesses, and cost, to name a few. Other physical traits such as melting points, water resistance, and UV resistance were also researched. The fabrication methods of these materials were also researched. These include 3D printing, cutting, drilling, etc. A waterproofing method for the drone frame and electrical components was researched and decided upon. A curable silicone-acrylic blend was chosen due to its ease of application, UV resistance, and ability to stay functional at temperatures of up to 200C. Three different frame design concepts for the project have been under works. The shapes and modularity concepts have been under revisions in order to formulate the best design choice. The modularity aspect of the drones is accomplished through the frame being divided into multiple separate sections as shown in the figures below in order to aid in the reparability of the frame if it is damaged.

One of the main difficulties we had when choosing materials to design the frame was finding reliable sources for the physical properties of materials. Some sources had conflicting data for the same materials. Sorting through this data was tedious and time consuming. In order to meet time constraints, our team had to narrow the scope of the materials that we were considering as well as narrowing down to the most important properties that we needed to consider.

By October 30th we plan to have a 3D model and orthographic view of our chosen design with dimensions included, and we will have calculated the center of gravity of our drone with and without the electrical components included. We will also have conducted a flexural analysis of the frame and the maximum force and energy impacts of the drone when flying at a maximum speed (30mph) to represent a worst-case crash scenario.

The 3 pictures below include a preliminary design for the shape of the drone frame and an orthographic view including the bumper designs for the drone frame. By October 30th we will have a proper CAD model and have done flexural analysis of the design.


Schematic 1 is what we're calling the "Butterfly Design", made of 2 sections of bumpers, 1 single top plate, one bottom plate, and one middle electronics bay.

Schematic 2 is a more ergonomic design which is designed as a one piece shell, containing all 4 propellers in that shell.

Schematic 3 is made of 4 individual sections, each holding a propeller inside. The propellers will be protected by a sandwich design that keeps the system intact.

Limited Technologies, Inc. 
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