HONU

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Drivetrain Challenge: Connecting the wheels to the frame

One of my earlier tasks was to design an interference between the wheels and frame in a matter that would remove all loads from the motor shaft. I was chosen specifically for this task as I was the person to identify a critical error in which the motor shafts at the four wheels would carry the weight of the robot, which would lead to failure.

Therefore, I designed a system with two bearings, a shaft, a shaft coupler, and a plate. The use of two bearings puts all the bending moments and the weight of the robot, which is around 50lbs or 12.5 lbs per wheel, onto the thicker shaft, eliminating the error. Furthermore, I also used ANSYS simulations to determine whether if the plate was strong enough and see potential spots of failure.

Testing the capabilities of our first prototype:

A majority of my first semester as mechanical lead went into creating standards for how the team would function and also testing the capabilities of the alpha prototype, and quantifying the requirements from the robot. In this video, we compared the speed we input into our software and the output speed of the robot.

However, we realized that our robot was not capable of turning. Our initial idea was to rotate the left wheels more quickly than the right to turn right and visa versa. We were unable to overcome the friction forces and turning one side faster only caused the other side to also be accelerated by friction. Hence, we then decided to implement swerving technology, which we worked on for all of my second semester as mechanical team lead.

To be honest, this was a very upsetting outcome if events for me. When I had just joined the team, a year and a half before this test, I had introduced the idea of swerve drive as I was skeptical of whether if our design would work, and I also wanted to take on the challenge of such a task. However, the team was unwilling to employ it as we would be introducing another complication to the already complicated design (the filtration system was our main innovation and was the focus of many members at the time). I now realize that I should have sought out expert opinions and talked to people with experience in building robots of similar size and pushed my idea harder.