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Summary (TLDR)
Summary (TLDR)
Researched and designed an innovative auger design with the goal of minimizing complexity and maximizing regolith excavation rate.
Problem Definition
Problem Definition
What is Lunabotics?
What is Lunabotics?
The NASA Lunabotics Challenge is a university-level annual robotics competition where students build tele-operated robots capable of excavating, storing, and transporting regolith(moon dust) simulant. The goal of the competition is to construct the largest regolith berm possible, while balancing robot mass, power consumption, and bandwidth.
The Two Robot System
The Two Robot System
In 2025, a rulebook change allowed for multi-robot systems. A two-robot system could maximize excavation time by splitting the task of excavation and construction to two separate robots rather than one robot responsible for both. The challenge with the two-robot system is designing it to perform reliably while minimizing complexity and maximizing berm volume. Between the construction and excavation robots, I was responsible for designing the excavation robot to fit these criteria.
UVA at competition in 2024
System Requirements
System Requirements
Meeting size and weight requirements are significantly more difficult with a two robot system. Fitting two robots in an envolope size of one robot constrains storage volume and excavation mechanism size. Additionally, a two-robot system requires two seperate drivetrains, regolith storage systems, and control systems, adding considerable weight.
Key System Requirements
Key System Requirements
The combined two-robot system must be contained within a 150 cm x 75 cm x 75 cm payload envelope
The combined two-robot system must have a maximum mass of 80 kg
The robot system shall be able to, starting with any part of it in the construction zone, traverse the obstacle zone until any part of it crosses into the excavation zone without failure.
The robot system shall be able to transport regolith across the obstacle zone without bulldozing
Technical Performance Measurements (TPM)
Technical Performance Measurements (TPM)
Shall have a mass of under 60 kg
Shall have an average regolith transfer rate of at least 8 L/min
Shall be able to build a 120 L berm in 15 minutes
Shall have an average power consumption of less than 240 W
System Definition
System Definition
Initial Idea
Initial Idea
After going through various ideas, I proposed the following two-robot system.
The two robots are stored vertically at the beginning of the run. The taller excavation robot has a gap inside for the smaller construction robot to be housed, to fit inside the size requirements.
A vertical auger on the excavation robot linearly digs down to collect regolith and dispenses it into a temporary storage.
The construction robot then moves underneath the excavation robot
The excavation robot uses a drop chute on the temporary storage to transfer the regolith into the construction robot
The construction robot traverses to the construction zone and builds the berm while the excavation robot simultaneously gathers regolith
Research
Research
In the real world, augers are commonly used to dig holes. Screw conveyors look similar and are commonly used to transport granular materials horizontally, vertically, or at an angle. The excavation mechanism combines an auger and a screw conveyor to simultaneously mine regolith and carry it into the intermediary system.
Different auger variations were researched, including the Siwertell auger, Archimedes screw, and vertical/angled augers.
Preliminary Testing
Preliminary Testing
I modeled different variations of augers in CAD to do preliminary testing in sand.
Vertical augers struggled to spin when filled up.
The friction is caused by sand getting stuck between the auger and the auger housing
We think that the friction was greater for the vertical auger because sand gets distributed through all sides of the auger, meaning sand gets stuck on the entire perimeter of the auger.
Angled augers spun more freely and provided constant sand excavation.
Preliminary testing proved that an auger mechanism is viable. We found that tolerance plays a significant role in auger functionality, which may make it difficult to manufacture.
Augers were modeled in OnShape and 3D printed on a BambuLabs A1 Mini
The Siwertell Auger design was abandoned due to it's complexity
System Definition Review Presentation
System Definition Review Presentation
During the SDR Presentation, I proposed the initial auger mechanism system for internal and external reviewer feedback. Multiple UVA faculty members were present who gave suggestions for improvement.
I delivered a full-system rough CAD of the excavation robot, as well as trade studies of different mechanisms. The presentation served as a way for the team to understand different proposed excavation robot systems.
Preliminary Design
Preliminary Design
Additional Research
Additional Research
Changes from SDR
Changes from SDR
Preliminary testing showed that an angled auger would be significantly more effective in consistently transporting regolith
So, the next iteration had an angled auger to minimize the risk of regolith getting trapped in the edges of the auger
Additional prototyping with a drill auger gave confidence in an angled auger. With an extended auger length, a vertical auger struggles to excavate consistently as the auger has to overcome gravity and prevent it from sliding down the bottom of the auger.
Concerns were brought up about being able to align the construction robot with the excavation robot when transferring regolith
So, instead of a gravity dumping mechanism, a back dump conveyor belt system would be used. The two robots would be placed outside of one another and would still fit inside the size requirements.
Converting to a back dump conveyor belt system also lowers the center of mass and reduces the chance of tipping.
The regolith will dump on the conveyor belt, and the conveyor will move the regolith to the back of the robot, creating space for more regolith.
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