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Flag Pole Linkage
This was a partner project for my robotics class. The objective was to build a linkage system with at least four links that created vertical linear motion representing Mario sliding down the flag pole at the end of every Super Mario Bros level. The motion was driven by a 12V DC motor, and there were no slots or belts to constrain the motion.
Ideation
My partner and I began our project by brainstorming some ways we could generate linear motion without violating the no slots and no belts project requirement. In this process, we each came up with a potential solution. We also decided early on that of our goals was to have a motor running continuously rather than oscillating back and forth between set angles.
Magnets
One idea was to put a magnet in the end of a link and use a magnetic flagpole to constrain the motion vertically. This was fun because it was an outside solution that constrained motion linearly without violating the constraints of the assignment.
Diamond Linkage and Arc
Most of the linear linkage systems we saw used only an arc of motion, so one of our ideas was to have a link that converted the full rotation to an arc and then using the resulting arc to create linear motion. In our final linkage design we accomplished the linear motion with a diamond linkage connected at its center to the arc.
CAD Model
Once we had decided on a linkage system for the project, my partner created a CAD model of the system and assembled the components. This allowed us to confirm the length of our linear path and generate DXF files to be lasercut.
Electronics and Physical Model
This project was run using a Raspberry Pi, an L289N motor driver, and a 12V DC motor. The motor was connected to power with a barrel jack plugged into the wall. We ran basic DC motor code slowed down using PWM control to protect the linkage system. To mount the motor I used a hole saw and a file to create a tight fit in a piece of 2x4. In addition to some woodwork, my partner and I did a lot of laser-cutting to create the front stand and acrylic links to our system. The links were held together with M3 bolts and lock nuts, and the lasercut pieces were nailed into the base.
What did we learn?
We chose to use a DC motor for our system to simplify the troubleshooting for our system as well as increasing the torque capacity of the motor. While the motor ran successfully, it still struggled to lift Mario up the pole. Additionally, we had a lot of troubleshooting issues regarding the DC motors. I had preexisting code that successfully ran my motor, however when I started testing the motor it no longer ran. This was strange to me but I messed with a few variables and eventually got the motor running again. Once the assembly was complete later in the evening, I rewired the motor to do final testing. Once again, the motor didn't work. I unplugged the electronics to test separately on my partners motor because I didn't want the motor to turn on at full speed and potentially damage the system. When my partners motor worked and I reconnected to the motor mounted to our project, that motor did not turn on. I had already checked that the motor wasn't burnt out, so this indicated that our DC motors were not compatible to run the same code, despite being the same model. This was a very interesting troubleshooting and learning experience, but eventually we got everything working and were satisfied with our final result!
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