This will cover the design portion of my UCLA Mechanical Engineering Capstone project, Kobe. The overall summary of the project can be found here.
Design
To begin the designing process of building a robot, our group had to first consider the requirements and parameters outlined by the professor. The two main mechanisms that would dictate the direction of our robot's design were the methods in which the robot interacted with the cubes scattered about the venue and the method of movement the robot would use traverse the venue (wheels were banned to add complexity). To explore different options and possibilities, our group brainstormed and sketched out three unique designs that utilized different methods of block interaction and chassis movement. I spearheaded the first design, which used four outstretched legs to traverse the venue like a spider and would locate, navigate to, and mark each wooden cube with a Sharpie. The second design had a six legged, insect inspired, movement system with a trough in front that would push all of the blocks into a designated area on the venue. The last design used a simple leg mechanism which relied on two rotating masses to inch forward to collect the cubes into a shaft until they were released as a stack.
Our group employed a Pairwise Comparison Chart (PCC) to objectively determine which design to continue to develop. This chart listed weighted factors that our group considered to be necessary for the development and success of the robot. After assigning a number based on how much each design met each criteria, a weighted average was taken, and the design with the highest aggregate score was chosen to be the direction our group would take in developing the robot. In the picture above, you can see that Design 3 had the highest total score, meaning that we would continue to develop Design 3. I couldn't help but be a little sore that my design (Design 1) ended up with the lowest score but ultimately reconciled its loss by admitting that the spider legs were rather ambitious and had the highest likelihood of failure. After some encouragement from my teammates, I was ready to contribute to Design 3.
After many discussions, the group determined that the most appealing aspect of Design 3 was its very simple movement mechanism. The movement system relied on a mechanism that only required one motor for each side of the chassis, making for a total of 2 motors. This was important because the provided board that would control the robot only had a total of 4 encoder ports, meaning that only 4 motors could be finely controlled. With the ability to traverse the venue using 2 motors, we were left with 2 motors to use in our interaction mechanism.
After going through another round of brainstorming interaction mechanisms, the catapult was decided as the most involved and would make for the most entertaining interaction mechanism. The implementation of a catapult was also very feasible with the given 2 motors so we developed this idea further. This mechanism would require one motor to launch the blocks and one motor to load the blocks. I hypothesized that the simplest solution to loading a cube onto a bed with only one motors was to simply push the block onto the bed of the catapult instead of lifting the cube, which to do accurately, would take more than one motor. And so the catapult system was added onto the walking mechanism and chassis, creating the more developed design you see on above.
After adding more of the required components to the model and running Finite Element Analysis on the chassis and legs of the robot, the final design was birthed. This design accounted for all of the necessary hardware that would be required to power and control the robot autonomously. Below is the final Solidworks model that would be used to construct the physical robot and keep track of all of the necessary components.
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