I've always been extremely passionate about sustainability; I believe that creating a more sustainable society, a more sustainable world, is one of the most important things for humanity to achieve in the upcoming years. With this passion and inspiration of mine, this past summer, I have been a member of the inaugural cohort of Punahou Sustainability Fellows. With this opportunity comes a responsibility to create a more sustainable world, and to use my resources, connections, knowledge, and skills to make the biggest contribution that I can towards this effort. 

Over the course of this past summer, myself and my fellow fellows traveled around the island, visiting different companies and organizations both dedicated to, and not, to sustainability; we visited companies in every sector of sustainability, from the energy sector (in the form of HECO, H-Power, Mililani Solar Farms, and many other locations), to the local agricultural sector (in the form of local farms and food importation facilities), to the transportation sector (in the form of interviewing leads of Hawaiian Airlines, and visiting transportation centers). From this experience, I learned the importance of biofuel development, and even the efforts that are going on here in Hawaii. From this, I learned that it is a grueling manual task that people must perform to harvest these biofuels on island, and the alternatives are large, gasoline powered pieces of equipment; quite obviously, neither of these methods are sustainable (both for the people, the economy, and the planet).

Thus, I thought it was necessary to create an automated piece of equipment. This will both create an easier harvesting process, and allow for decreased carbon emissions in this sector of energy production and biofuel research and development.

I understand that it may not be extremely clear how this project is related to FTC Robotics, but this is a legitimate goal for this project, and the process that I am going through to create this project. 

I am currently on the team 6962 Pokebolts for FTC robotics, which has recently won the Hawaii regional to advance to worlds. However, I feel that my contribution to the team could be greatly improved for the next season, and I use project such as this to improve my CAD and design skills. Additionally, through this project, I am hoping to improve my programming ability, potentially even becoming a contributor on that end of my FTC team. 

The primary goal of our first iteration was to create a viable prototype for a differential drive system, which would be both sturdy and reliable. This first iteration aimed to create a visual ideation of what a differential drive system could potentially look like, and what mechanical systems would need to be developed to create a system with the aforementioned properties (sturdy and reliable). However, this first version was never meant to be a final prototype, or even turned into something with properties similar to a final prototype - it was merely a learning experience. For this first iteration, it was primarily focused on the development of the internal gear mechanisms. 

We realized that this design had many major flaws, some of which we ignored in our next prototype (we heavily regretted this), some of which we acknowledged and designed to improve upon. 

The first of the flaws that we acknowledged was our extremely small gear modules, something that was sure to break under the immense loads that this module would be placed upon. Secondly, our couplings and shafts, specifically on our large drive shafts, didn't meet any industrial standards, and would have to be custom machined - thus, this should be changed to be something that can be COTS purchased. Finally, the assembly of the internal gear, as we found, was extremely tedious at times - specifically with the assembly of the outer gears, the threading, and the insertion of nuts into extremely small spaces. 

The first of the flaws that we did not acknowledge was that many of the parts were extremely hard to manufacture in shop, and would either have to be 3D-printed out of exotic and expensive materials, or would have to be outsourced to be manufactured in a professional machine shop (as they required 5-axis milling, but could actually be prototyped). Secondly, we refused to acknowledge that the differential system added a lot of mechanical complexity, and had many intricate, hard to access points of failure, which could lead to catastrophic breakdowns, and extremely difficult repair processes (neither of which are desirable). Finally, the differential system had zero potential benefits that we could utilize - we had some concerns regarding the torque required of the secondary gearbox, and the speed required of both gearboxes, and realized that it was going to be a better solution to use a differential steering system, rather than a differential gearbox (a gearbox dedicated to each side of equal power). However, as we chose to ignore these problems, we began our next iteration of our drivetrain still pursuing a complex differential gearbox system. 

As previously mentioned, the primary purpose of the header was to create a system capable of harvesting and intaking all of the raw biomass and biomaterial. For this system, I ideated a system involving funnels directing stalk a few inches off the ground into a row of rotating blades, which would slice the stalk. The stalk would then fall into an auger system, which would drive all of the raw biomass into a center intaking converyor system. The rotating blades would be a mechanically linked system, using a single geared up motor and a system of belts and chains to properly connect all of the power between different blade systems. 

While we have not gotten the chance to test this prototype in the field, we have received some substantial feedback from the staff at Kuilima Farms. While our design is not the traditional system of oscillating blades, they said that it is potentially viable system, while not traditional. However, we would prefer to switch to creating a system which would involve oscillating blades, since I believe that trusting an industry standard for small scale harvesters is better than venturing with our own intuition. 

In regards to our design, we realized that we should create better design practices in regards to greater vision - we should see the greater picture of the entire assembly before starting designs, even with smaller parts of the project such as this. 

Learning (partially) from our previous attempt. we made a few modifications to this upcoming iteration, which we restarted from the ground up due to a flaw in our design that would completely break everything with the changes that we intended to make. 

First, we increased the module of our gears to increase the stability and rigidity, and made the full commitment to either outsourcing manufacturing of the gears, and/or exotic 3D-printing of the required parts. In this, we created a herringbone style design, which allowed our gears to boast self-alignment features, quieter operation, reduced backlasher, and greater tooth engagement (opposed to normal spur gears). Second, we changed our coupling systems and gearing systems to use COTS parts, specifically designing around motor mountings and proper usage of chain. Finally, we further focused our design of our internal gears for ease of assembly and disassembly, something that we should have adopted from the start. 

Regarding the other flaws which we did not fully acknowledge, we further exacerbated the issue of manufacturing our gears out of sufficiently rigid materials, by committing to herringbone style gears, which would require either 5-axis milling or exotic 3D-printing. Additionally, we chose to stick with the differential gearbox system, but did reduce the complexity of the required gearboxes by utilizing chain in the connections. 

It was after the completion of this iteration that we realized that using a differential gearbox system was a non-viable route. It provided very little benefit, for a lot of extra complexity and manufacturing cost, and using a differential steering system was a far simpler, cheaper, and more viable path to take. Realizing that it was time to change course, we decided to cut our costs and the time sunk into this design in favor of the more viable (and much more simple) differential steering system. 

However, we still look many of the lessons that we learned from this experience with us. Moving forwards, we planned to avoid having custom complex parts (such as gears, sprockets, etc.), and use as many sparts created by FRC manufacturers as possible. FRC manufacturers were chosen because it eliminates much of the time and energy needed to produce these parts, and it also ensures reliability and stability in components. 

With this in mind, moving past this point, we decided to standardize the equipment that we were using for the entirety of this project, primarily the bearings, motors, shafts, collars, gears, and chain (1/2" Hex Shaft, Bearings, Collars, Gears, and #25 Chain).  This part standardization allows us to adjust our designs much more freely once parts arrive, as we will not be waiting on specialized parts to arrive (upon modification). 

From this experience, we also learned the value of FEA; we can now accurately predict points of failure in our design, and understand when, where, and under what loads our parts will fail. With this newfound ability, we can better test and simulate structural loads in our designs to ensure rigidity, stability, and the desirable ruggedness. 

Finally, I learned that in order to avoid expending unnecessary and extra effort, avoid pocketing the plates before the basic plate geometry is finalized - pocketing early has the tendency to break the assembly, part-studio, and render FEA useless; consequently, the pocketing has to be redone, along with all following features based off pocketing. 

A major part of this new iteration was rethinking our power draw. Previously (and I know this sounds really dumb), we weren't super conscious of the power draw that would be required of the drivetrain, thinking that as an alternative, we could always run our motors at lower RPMs to save power.

However, looking at efficiency curves, torque outputs, and the sheer current draw that would be required, we had to completely rethink our system of power. With the help of our advisor, Mr. Baffoe, we created spreadsheets to calculate the ideal amount of motors at a specific gear ratio to achieve the speed an acceleration we needed. These spreadsheets factored in the different amounts of friction, efficiency, energy loss, torque, and speed requirements to calculate the ideal amount of motors at the ideal efficiency. 

In regards to the speed and acceleration, neither of these values were extremely high, and were in fact, extremely low, only around 0.25ft/sec, and 0.125ft/sec^2. Thus, since there was such low speed and acceleration requirements, and power draw was a significant issue with the previous iteration, we realized that we can reduce the amount of motors, and simply just gear them up. Since the only thing we really needed from our motors was high amounts of torque, we decided after our calculations that 2 CIM motors per side running at high efficiency, and geared 60:1, would be sufficient propulsion for our robot.

The introduction of an extremely high gear ratio gearbox was one of the most innovative parts of this design. For this design, we chose to package our gearbox as an extrusion from the main plate, connected by shafts, t-slots, and plates. This gearbox utilizes COTS gears, specifically from FRC, #25 chain (2:1 reduction), and Versa-planetary Gearboxes (30:1 reduction) to achieve our desired reduciton. However, as clearly shown below, this gearbox is pretty big and clunky, and could definitely work to have its size reduced. 

While this design was a major improvement over the previous one, there were still many improvements that needed to be made. The first major improvement that needed to be made for the next iteration is the shrinking of the gearbox. The gearbox, simply, is far too big, and can be significantly reduced. The plan to achieve this was to angle the motors off-center, and collapse them closer together to create a more triangular profile (for which, 2 vertices would be motors, and 1 vertex would be the output). In addition to this change, we also contemplated switching the motor power train to the output shaft to sprockets instead of gears, but were uncertain due to the horizontal tension placed upon a cantilevered motor. Adding a cantilever support is a potentially viable solution to this, but in the end, adds a significant amount of effort or complexity to this system which is designed around simplicity. 

We also learned some lessons about cost - simply put, it would cost too much to structure all 4 of our plates out of aluminum, and thus we turned to acrylic. Our outer plate is not being used for any structural loading, and thus does not require the same amount of strength that our inner plate does. For this reason, we chose to switch courses, and change out outer plate to acrylic, which will simply act as an outer deflection shield against any weather or debris - for this, 1/4" acrylic should be more than enough. 

Regarding the overall chassis shape, however, this was very close to finalization, as I was closing in on a shape that was both functional, and aesthetically pleasing. One of the final changes that would need to be made was the pocketing of the inner plate to reduce weight, which I was not sure was necessary, as the inner plate only weighed around 15lbs. 

From the previous iteration, we first learned that we needed to reduce our gearbox profile in order to increase and maximize space efficiency. To do this, I decided to angle the motors, moving them as close together as possible. Additionally, I reduced the tooth count on the gearbox gears, thus shrinking the distance between each individual motor and the output gearbox. These changes resulted in an angled gearbox shape, similar to an arrow. While it still used the same fundamental principles, the geometry of the gearbox has been optimized for space and compactness, further pushing it into the plates, while still saving room for the necessary wiring. 

The creation of custom sprockets is also something that came along with this prototype. While these are not sprockets for the chain (we are using COTS sprockets), these are still equally as vital to the functionality of the final robot. These sprockets are designed to be the carriers of the bottom tracks. To prototype these, we plan to cut the sprockets out of 1/4" aluminum, and then use a central mounting bracket to connect the different sprockets.

• 4'x8' Acrylic Sheet

• 4x 40:1 VersaPlanetary Gearboxes

• 4x CIM Motors

• M8 Heat Set Inserts

• M8 Bolts (Misc.)

• M6 Heat Set Inserts

• M6 Bolts (Misc.)

• M6 Heat Set Inserts

• M4 Bolts (Misc.)

• M4 Heat Set Inserts

• M4 Lock Nuts

• PLA

• PETG