The third project we were instructed to do was to complete a "Motor Speed Control" project where we had to design and manufacture something that moved using a motor through closed loop control. Specifically, we had to create something that would transport a 1'' x 1'' x 12'' aluminum block across ten feet. The block would be supported by its bottom face only. The goal was to transport the aluminum block as fast as possible without it falling over. We were also given a 12V motor, arduino, and adapter which would drive the movement.

 

This project consisted of two main parts. The first part consisted of creating a CAD assembly of the design and then performing a motion analysis on it using Solidworks which would simulate the angular velocity and time it would take to transport the aluminum block. 

 

Before CAD-ing, I sketched out my design ideas. I figured that wheels would be a simple, yet effective way of transporting the block. In addition, they would help balance out the weight made by the wheel. The wheels were linked together with a crank and axle. The shaft of the motor was used as the axle for the front left wheel, allowing it to spin forward, which would naturally propel the other wheels forward.The middle of the axles had cylindrical extrusions which would be fastened to a platform that would support the aluminum block.

 

 

 

 

 

 

 

 

The next step was to CAD and create a motion analysis. Based on the simulation, the system that I had designed accelerated to 1440 degrees/second and had traversed ten feet in seven seconds, which was very quick. This made sense considering the symmetry of the design and the use of four wheels, which allowed it to move quickly without it falling.

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ZIP Files for Assembly, Motion Analysis is titled "Motion Analysis 6": 

https://drive.google.com/file/d/1fRsdw9ky7ZGknFmG7d-3uVC7GPm_-7Dw/view?usp=sharing

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In the second phase of the project, we had to create a physical prototype of our design and test it to see if it matched the results of the simulation. I worked in a team of 3 where we all pitched our own designs. At the end, my design was chosen.

 

When it came to manufacturing the parts, our primary method was 3D printing. We first went ahead and changed some of hole dimensions to account for tolerances. Since we were planning to use fasteners, we added holes to allow for tapping and fastening of screws.

 

After receiving our 3D printed parts, we got to assembling. While the wheels had holes big enough to fit the axles, we ran into a couple of issues. First of all, the wheel attached to the motor shaft was very loose which would make it difficult to produce consistent motion compared to the Solidworks model, where the components were perfectly concentric. To resolve this issue, my teammate and I stacked layers of heat tubes on the motor shaft and slightly shrank them with a heat tube. This created an extension to the motor shaft and "increased" its diameter to allow for the wheel to tightly fit in. Another difference we spotted between the design and the physical prototype was that the cranks could interfere with the motion of the wheels. In general, the wheels were secured to the axles using nuts. When it came to fastening the cylindrical portion of the axles to the platform, the screws wouldn't fit in completely after tapping them. As a last resort, my teammate decided to use a glue gun to attach the components to the platform.

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In addition to manufacturing, code was written to program the motor, which was wired to an arduino, to accelerate up to a certain speed and then deaccelerate it by the time ten feet was reached.  

 

After assembling both the mechanical and electrical components, it was time to start testing.

While the assembly moved, sometimes it would skid off to the side. To resolve this issue, we added rubber to our PLA wheels and rechecked our wheels to ensure that they were freely moving. When the code ran at the velocity given by the motion analysis, the aluminum block would fall, clearly showing that the motion analysis did not accurately reflect the physical prototype. As a result, the code had to be modified a multitude of times to ensure success. Eventually, we got there, with a run time of approximately 26 seconds, and output voltage of 35.

 

 

 

 

 

 

 

 

 

 

 

 

 

Lessons Learned

      When it came to testing the wheels, the movement was often inconsistent. Sometimes the wheels would move straight, and sometimes, they would immediately skid off to the side. I believe a big reason for this problem was that we chose to use our 3D printed wheels. If we had decided to use rubber wheels instead, which would generate more friction, it would've saved us a lot of time. Since we used glue guns instead of fasteners to assemble some of the components together, this made our design more asymmetric which resulted in us having to changing the motor's angular velocity. Next time, I would definitely prioritize fasteners.

      In general, I also learned to be more patient. There were times where I worked for a couple hours with little to no progress, and it was easy to erupt in frustration. However, by eventually learning to be more patient, it gave me the focus and calmness I needed to eventually complete the project.