LunaBotics

Lunabotics was a NASA moon rover design competition that my roommate and I spearheaded at our college. It was ultimately put off due to COVID, however we were able to present our robot through a webcam meeting to the judges. 

The mechanical design began at the wheels with the drive system. 

The wheel assembly is powered by a brushless DC gimbal motor with a 900w power rating. plenty for our application. There is also a 600p rotary encoder for position monitoring of each wheel. 

Both the motor and the encoder are connected to an Odrive to allow for a closed loop control. 

The first wheel design I came up with used a double leaf spring design to provide flexibility between the wheel rim and the hub motor. The mount connected to a single 2020 extrusion was also bad and had to go.

After abandoning the leaf spring design I started to experiment with rigid wheels using a hexagonal pattern in place of traditional spokes. This was the design I settled on.

Due to the size constraints, I decided to take on the challenge of designing a wheel deployment system to artificially give our rover a larger wheelbase than competitors. The system uses servos on each wheel to release a four bar linkage that is propelled by a constant force gas spring of 40lb on each wheel.

Here is the frame with all four wheel assemblies attached.

Once the frame started to take shape, I began working on the digger. 

The digger is a bucket lift excavator design powered by a 4KW BLDC motor through reduction belts. The entire assembly can drive itself up and down on the pivot gear that controls the angle using two lead screws. 

I started by making a planetary gearbox to drive the helical T8 lead screws.

This gearbox is scalable and worked surprisingly well on the first try. I would reuse this component in later parts of the robot's design.

The 3D printed buckets have metal blades on the edges and attached to roller chain in regular intervals.

Here is the final product before we left for COVID