VEHICLE
Time Period: April 2017 - May 2017
Course: Prototyping and Fabrication
Skills Developed: Design Thinking, Problem Solving, Laser Cutting, 3D Printing
Software: Adobe Illustrator, Arduino, Adafruit Bluetooth App
Project Background
The task for this project was to brainstorm, design, prototype, test, and iterate to produce a vehicle with a partner. It was a six week project with one prototype due each week, each more advanced than the previous one. There were no restrictions regarding the design other than that it could not have any motorized wheels and must be controlled by Bluetooth. My partner and I wanted to create something unique, so we decided on a cart that almost looks like a bug crawling. We encountered many complications along the way but I believe we created something amazing. At the end, the vehicle must traverse an obstacle course that was unknown until the day we presented it at the Jacobs Design Showcase.
WEEK 1
Proof of Concept
We began this project by doing some research into how to make things move without using gears. In the end, we decided to focus on a system that had to “wheel” like components with another attachment for steering that the references below inspired us to design.
We created two different models. They coincidentally turned out to be very similar mechanisms. One involves two crosses rotating about an axis, and is a simpler design. However, we were not 100% sure that the crosses do not count as wheels, as the definition of a “wheel” was rather vague at the time. The other has a pair of circular legs that rotate to move through space. It was trickier for us to design; however, it is a more interesting design, visually. Ideally, it would move like a kangaroo in a way, bouncing from the circular legs to the front nose, but we are not sure if it would work as is, if we attached the servo now.
WEEK 2
Electronics Assembly
This week's task was to assemble the electronics which included: Motor Shield, Prototyping Shield, Adafruit Bluetooth Module, motors, and an Arduino microcontroller. Our first step was to determine how our vehicle would move, how many motors we would need, and how these motors would turn.
I took charge of soldering. Soldering the headers and wires that connect to the headers that plug into the Arduino and the header in which the Bluetooth sits on the prototyping shield, was much harder because there was less space to work with. However, once all this was done, we simply stacked our Prototyping Shield on our Motor Shield and those on our Arduino and connected the motors to the motor shield.
I found many samples of code so we sat down and played around with different Arduino examples to try to understand how we should implement the code to make the motors turn. However, after extensive research and adjustments, we were unable to compile the code; realizing a syntax error was causing all these problems, we performed more research to adjust the syntax, but it still did not compile. After more debugging, we finally found another issue: we needed to define the motors earlier in the code.
From there, we discovered that the system was unable to complete the factory reset. We diagnosed the issue to be in the motor shield and fixed some of the solder connections on it. After a lot of frustration, the module was finally able to reset and compile.
WEEK 3
Chassis Prototype
We took our electronics from the previous week and created a chassis to move our vehicle. We realized that our initial chassis prototype was not going to work, because it could not turn. So, we modified the design, adding two "wheels", increasing stability and the ease of motion. The steering was then controlled by each side of the chassis, so powering just one side turns the whole vehicle.
By adding two semi-circles, we also needed a way to power them. We did not want to get two more motors, so instead we created a gear train to transfer the rotational motion backwards, to the other two “legs”. We had several issues connecting the motor to the gears. Initially, we 3D-printed a motor hub, but eventually we found that using a smaller gear on the motor shaft to power the larger gears of the gear train would optimize torque and reduce speed.
Encasing the motor was also challenging. We added scraps of wood to create stability, but it was not enough. Sometimes the gears got stuck or misaligned. Unfortunately, this iteration had some trouble moving backwards, left, and right.
WEEK 4
Prototype Refinement
After the last iteration, we realized we needed to redesign the “C” legs, the gearing system, and electronics housing. We also needed to reorganize the components and make our product lighter.
Our project generally had a round theme. So, we modified the “C” legs adding circles to the bottom which would also help to keep the legs from getting stuck when going backwards. We also decreased the number of gears and enlarged them to reduce friction and get more torque out of the motors which we relocated to the middle of the three gears. We added another wall to align the gears more. Finally, we made a wider and longer base to easily fit all the components and maintain the rounded shape.
We decided to try using screws instead of dowels to hold our gears in place, which turned out to be a bad idea because they could not be attached or gripped as well by some of the components. Attaching all the components to these screws required a lot of problem solving, glue, and excess parts.
Once everything was assembled, nothing moved. All the lights were on but the motors would not budge. We diagnosed all the electrical components and eventually found a loose wire. So we fixed the solder and after testing it, the motors worked nicely again.
WEEK 5
High Fidelity Vehicle
At the beginning of this iteration, we took a step back and looked at our projects from the past two weeks, analyzing what worked and what didn’t combining the good aspects from both attempts in hopes of getting it to finally work.
Due to minimal friction, the legs kept slipping and were not able to pick up the chassis as they rotated. We resolved this by adding rubber bands around the outside of each leg. The slightly flat shape at the edge of the legs stopped the vehicle from moving backwards. We fixed this by rounding the edges more so that the legs would not get stuck when the flatter surface approaches the ground. One of the biggest issues was that our gears were not aligned. By enclosing doubled-up gears inside a wall and leaving a slight amount of room between these walls to relieve the force and friction resolved this. Another issue we discovered was our attempt to use screws as dowels and use small metal washers and nuts to hold it in. So, we returned to wood dowels and metal washers with a bigger outer diameter and thickness to reduce friction between gears and the wall. There was not enough power being delivered to the motors contributing to why the motors could not lift or push the vehicle. We added a battery pack increasing the voltage from 6V to 9V. The last issue was that once we got it running, the chassis seemed to hit the ground hard as the legs got to the open portion facing the ground. We resolved this by adding some felt underneath the base which softened the impact a lot. We later obtained plastic stoppers to replace the felt in each corner of the base.
Along with addressing those issues, we wanted to make our chassis more visually appealing. We designed patterns for the base plate and the walls. This not only gave the vehicle an edgy caterpillar-like, butterfly-like look but also reduced the weight of the chassis.
Obstacle Course
WEEK 6
During the Showcase, our vehicle had trouble recognizing commands and responding to them through the Bluetooth system. We tried to diagnose the wires like before and eventually noticed that one of the wires came loose again. So, we soldered it back more tightly and the product returned to running perfectly. We were finally able to complete the obstacle course, easily.
REFLECTION
Starting out extremely basic, I had no idea what the finished product would look like or how it would work. However, I am extremely proud of how this vehicle turned out. Throughout the process, I encountered many obstacles and felt everything from confusion to wonder to disappointment to pride.
It was a little intimidating at first knowing that we would have to make significant changes to anything we found online. The week after we made enormous changes, which ultimately failed, I felt like we had taken steps backward in the process, but these mistakes made it clear what about our design needed to change in order for it to work effectively. On top of that, we had several weeks of a model with little to no functionality, but with persistence and problem solving, we were able to create a robot that moved in a successful, controlled manner. Overall, I am very proud of what I accomplished. It was a stressful yet rewarding experience.
I learned a lot about design: from ideation to prototyping to testing, it was all a huge learning process that I really enjoyed. Being able to evaluate my project and iterate on it to improve the design and function is a great, and fulfilling experience because I feel like I am taking my design to its full potential. I hope to use the skills I developed through this project including laser cutting, Arduino, problem solving, etc. in the future in school projects and in industry.
If I were to do this again, I would probably do something completely different, but this does not mean that I am unhappy with the design, only that there are so many options that it is impossible to choose a “better” idea. I would like to explore other designs for "wheels". Overall, the whole process taught me that producing a fully thought out design takes many hours and many iterations, that all lead to something amazing.