Ryan Bao

Robobuggy

Buggy is a competition where human drivers steer a gravity and human-powered vehicle through a course. The buggies can go to speeds of 30+ miles per hour and have to go through several tight turns. The goal of the Robobuggy project is to build a robot that can follow all Buggy rules and guidelines and autonomously maneuver through the course.

Current World Record (Autonomous Buggy)

The robotic buggy that I helped build is the current world record holder for the fastest autonomous buggy, with a time of 3 minutes, 9 seconds, 70 milliseconds. We crashed zero times, another world record.

Mechanical Design

Designed electronic mounting to dampen vibrations. Mounting was designed to be fully waterproofed and adequately cooled
Designed back wheel mounting system to be adjustable to ensure parallel back wheels
Designed push-bar mounting
Led fabrication of all machined components

Back Wheel Mounting System

For the back wheel mount, we needed the axles to be connected to encoders for localization purposes, and we needed the wheel angles to be manually adjustable in order to align the wheels. In order to accomplish this, we took inspiration from car wheel mounting, and designed around that.

This system uses two turnbuckle-style connecting rods and corresponding ball-end joints in order to adjust the wheel angles. This entire system mounts on top of the buggy frame.

The axle was the most difficult part to design. The wheel is designed to be mounted onto the right side of the axle, and is clamped down using the larger threaded part. The axle also uses a keyway, which has a corresponding keyway on the buggy wheel. The other side of the axle is designed to fit through the encoder, and uses a thread and nut to hold everything in place. One major problem we had designing this axle was the large stress concentrations on the areas where the diameter changes, so we supported those areas with bearings. One particular area of concern from the FEA was the part directly to the left of the wheel mounting (largest diameter) area, so we took special care to increase the diameter of that area.

Pushbar Mounting

The pushbar mounting had to fit onto the frame, which was difficult because the new frame is considerably thinner than the old frame. As such, we had to use thinner u-channels to mount the pushbar. This forced us to use unconventional mounting methods as shown.

The material we selected was aluminum, simply because it was easier to source this size u-channel made of aluminum, whereas steel u-channel of this size would have had to be custom-made. We ran simple FEA studies to ensure that the aluminum wouldn't fail under normal buggy conditions. However, the push-bar, which is much longer and thinner than the mounting mechanism, was made of steel. Because the cantilever was much longer, we decided to use this stronger material. In addition, this steel tubing was much easier to source.

Carbon Fiber Wet Layups

The normal construction of buggy shells involves carbon fiber wet layups over a mold. Because Robobuggy is not a standard buggy team, we had to adapt the standard shell-making process to our needs. I participated in the shell-making process in the following ways.

Helped make the rough mold by laser cutting foam slices
Helped finish the mold with spackle, Bondo and sanding
Led wet carbon fiber layups
Helped finish the shell

Fabrication

I was primarily responsible for fabrication because I have access to more campus tools than most of the team. During the fabrication process, I was able to practice programming CNC tools such as a large CNC router and a CNC milling machine. I was also able to practice manual machining, including processes that I was relatively unfamiliar with such as boring, and finishing processes such as sand blasting.

CNC Milled Part, five processes and six tool changes, AISI 1018 steel on a HAAS Mini Mill

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