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by
David Kohanbash
on
May 15, 2023
Introduction
The DARPA SubT challenge required drones to be designed for flying through tunnels and exploring unknown subterranean environments. To achieve this, we designed a custom drone that was purpose-built for the challenge. In this article, we will explore the design and development of this drone, including its specifications, components, and features.
Design and Development
The drone was designed to be as aggressive as possible in order to explore difficult environments as fast as possible. However, this aggressive design came with the risk of crashes during testing. To mitigate this risk, we used a modular frame where any part could be easily swapped if it got damaged.
The heart of the drone was the Pixracer controller, which took commands from the computer in the sensing payload and executed them. From there, the Electronic Speed Controllers (ESCs) would commutate the motors. The motors had to be replaced every few months during testing due to dust ingress and the wear and tear on the internal bearings.
Initially, the drone was developed without the top cowling. However, this cover/cowling ended up being needed to increase rigidity in the frame. A few times we saw poor drone performance and were able to trace it back to increased vibration from the cowling mounts to the frame being loose. The cowling was a custom carbon fiber layup that mounted to each of the 4 motor mounts as well as the center section.
Specifications
Specifications
Type: Custom Quad-rotor X-frame
Size: 830(L) x 770(W) x 350H) mm
Weight: 6.2 kg (13.7 lbs)
Power: 326 Wh (22000 mAh, 14.8V 4S LiPo)
Speed: 5+ mps
Endurance: 13 min
Prop Guards
As we started flying faster through increasingly small openings, it became clear that better prop guards were needed. The initial design had prop guards just right above the props, but we had to add prop guards below the props as well. The prop guards were made from a thin carbon fiber with a birch core. In addition to the “hard” prop guards, we wrapped a string in the front and back to bridge the prop guards to increase the ability to “bounce” off from items and not cause the drone to crash.
Crash Recovery
As we mentioned earlier, the drone was designed to be aggressive, which came with the risk of crashes during testing. To recover from these crashes, we used a modular frame where any part could be easily swapped if it got damaged.
Conclusion
In conclusion, the design and development of this custom drone for the DARPA SubT challenge required careful consideration of the drone’s specifications, components, and features. The drone’s aggressive design and modular frame allowed it to explore difficult environments quickly and efficiently, while its prop guards and crash recovery system helped to mitigate the risk of damage during testing.
Frequently Asked Questions
Q1: What was the purpose of the drone’s aggressive design?
The aggressive design was intended to allow the drone to explore difficult environments quickly and efficiently.
Q2: Why did the drone’s motors need to be replaced every few months?
The motors needed to be replaced due to dust ingress and the wear and tear on the internal bearings.
Q3: What was the purpose of the drone’s prop guards?
The prop guards were designed to protect the drone from damage during flight and to help it “bounce” off from items and not cause the drone to crash.
Q4: How did the drone’s modular frame help with crash recovery?
The modular frame allowed any part of the drone to be easily swapped if it got damaged, making it easier to recover from crashes during testing.
Q5: What was the drone’s endurance?
The drone’s endurance was 13 minutes.
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