16. Applications & Implications
In this week's work, I intended to formalize the proposal for my final project!
According to the requirements given by the FabAcademy, my project should incorporate:
- 2D and 3D Design
- Additive and Subtractive Manufacturing Processes
- Electronics Design and Production
- Embedded Microcontroller Interfacing and Programming
- System Integration and Packaging
Additionally, it is stated that as much as possible of my project should be manufactured in-house, which makes everything more challenging.
As already shown on my Final Project page, I intend to design, build, and assemble a three-wheeled electric scooter, which is designed for the commuting routes from nearby student homes to the campus in my university area.
The campusROVER, the name and branding I want to carry the project under, is my biggest engineering challenge yet, as I have no previous experience with any kind of vehicle systems. However, I am confident that I will be able to pull it off in some way or another.
Answering some questions:
FabAcademy proposes a series of 10 questions for the final project plan. When properly answered, they should establish a well-defined path to follow.
1. What will it do?
The three-wheeled electric scooter design should be self-propelled by an electromechanical system comprised of two DC motors mechanically connected to the rear wheels. The scooter should be able to easily change its direction and have a structure that can withstand a weight of at least 80 kilograms. Electronic control of the motors to change their speed using a throttle lever should also be possible; this electronic control should display information about the vehicle on a dashboard.
2. Who's done that beforehand?
Using the search bar provided on the FabAcademy website, I came across some projects from past years. Although I wasn't able to find an exact match for my project, there are many projects about vehicles that incorporate methods or mechanisms similar to what I have in mind:
- "The Monowheel" by Christopher Dos Santos.
- "Press Fit Go-Cart" by Andrew Mao.
- The closest match was this two-wheeled electric scooter by Ivan González.
Nevertheless, none of the projects I found had the complexity I intend my own project to have, so in this case, I have to start from scratch in many aspects of it.
3. What will you design?
A lot of things have to be designed for this project. First of all, I have to find a way to move the scooter, also known as "The Powertrain," which should be comprised of the motors and some kind of transmission to get the power from the electric motors to the wheels. It needs to be sturdy enough to handle the torque and speed required to move a 90kg person at at least 10 km/h. Another design challenge is to create the chassis and the driving handle for the scooter, which should be able to carry a 80kg human and confidently steer the vehicle. Yet another challenge is the electronic system for the scooter, which should be able to control and handle the high currents demanded by the DC motors and do so safely and reliably, while also displaying information on the dashboard and monitoring the battery.
4. What materials and components will be used?
Since it's cheap and easily accessible, I will be using some steel framing for the main chassis, along with some 3D printed parts in PLA plastic for the driving handle and the powertrain assembly. The electronics carry the most complex pieces of design in this project, and the greatest amount of individual parts, which range from simple resistors and capacitors to complex MCU's and other integrated circuits. Some thick plywood will also be necessary to fabricate the board on which the rider will stand. Additionally, I need some kind of braking system to make the product usable and safe. The carefully thought-out Bill Of Materials (arising also from trial and error) corresponding to this project is displayed here: See the BOM.
Due to the large amount of individual components, I have divided the BOM into eight categories, according to the nature and function of the part inside the electric scooter. Also, you can divide parts by section of the proyect (Powertrain, Chassis, Drivetrain, etc.). I have also implemented a ID code system in order to find specific parts of the BOM according to their names in the file repository (where you will find all the original design files), and complimentary assembly diagrams.
The BOM also includes the price for each part, which already answers question 6.
5. Where will they come from?
When managing these kinds of complex proyects under tight deadlines, I always like to use local providers as much as possible, because local means readily available in case something goes wrong and need another piece / material ASAP.
6. How much will they cost?
Answered in question 4 with the Bill of Materials!
7. What parts and systems will be made?
Almost everything on the scooter will be manufactured in-house: The chassis, the electronics, the mechanical systems, the driving handle, the throttle and braking levers, the decorative parts, etc. What will NOT be made by me and will be bought pre-made instead:
- Braking Pad Assembly and Brake Disc.
- Rubber Wheels
- Battery pack and DC Motors
- Rowlock and ball-bearing assemblies
- Some sensor and display modules.
- PCB's*
* PCB's will not be fabbed in-house, but instead using a PCB Manufacturing service, which for my requirements results in much nicer finishes, quality, electrical properties and ease of assembly. Nevertheless, all PCB's will be designed by me.
8. What processes will be used?
For this proyect I will need to use the following design / manufacturing processes:
- CAD 3D and 2D Design
- PCB Design
- 3D Printing
- Laser Cutting
- Metal Cutting & Welding
- PCB SMD Soldering
- Woodworking
- Spray Painting
9. What questions need to be answered?
Since I have never done any kind of vehicle before I need to answer the following:
- How can I control large inductive currents reliably?
- How do I transfer power from the motors to the wheels?
- Can I design capable mechanical systems using only 3D printed parts?
- How do I do electric arc welding?
- How can I mount a braking system designed for bikes?
- How mechanically capable can 3D printed parts be?
- How do I reduce friction in all the moving parts?
- How do I measure rotational speed?
10. How will it be evaluated?
Once this proyect is finished, I will need to evaluate its performance in these different aspects:
- Maximum speed testing
- Braking distance testing (from max speed to 0)
- Weight carrying capability
- Autonomy on a full battery charge
- Tough terrain capability
- Power consumption
- Thermal Behaviour (Electronics System)
Thank you for taking a look into my 16th week's progress!