Robotics 1

Define: We were tasked with making a minibot, which is an accumulative assignment of all that we have been learning. We had to design a small 4-wheel/2-motor minibot on a drive base programmed with Arduino to surpass a obstacle course.

Initial Concepts and Design Sketches/CAD

In this image, we were trying to visualize what it would look when we added all the necessary parts. This includes the sprocket, board, wheel, and e-clips. This is not drawn to scale, rather, a rough drawing that helps us understand what goes where. We added measurements which would aid us later on when lathing. We used some test board to sketch this out because we were able to prop it up whilst lathing, it was a fun little hack!

This image shows our initial hex shaft design, we had to reiterate upon this design several times which you will see in the "testing and iteration" section.

Testing and Iteration

This is our new test board with the new measurements. We realized our mistake was that we double counted cuts, even though the measurement already accounted for this. To fix this, we simply subtracted the values from our measurements.

Another thing that was difficult was getting the wood to stay in a right angle when building the drive base. To solve for this we used clamps to hold our work together.

This is the widened hex shaft. As you can see, the sprocket fits perfectly and the eclips are easily able to attach onto the cuts.

Another issue we ran into was that we were using a double sprocket on the motor and having the two sprockets of the wheel shafts connect to that via a chain. The only issue was that when latheing, we lathed under the impression that they would be at the same level. When in reality, the double sprocket has a top and bottom sprocket. This cause the chain to stretch at a funky angle. To solve for this, I relathed the back wheel's shaft so the slot for the sprocket matched with the higher sprocket in the double sprocket.

This is another iteration we made to our minibot. Initially, our chains were too loose and had to much slack. This caused the chains to slip off while testing. To solve for this we put nails and screws in to extend the area the chain had to go over and effectively tightened the chain.

Another thing we noticed while testing was that the electronics moved around a lot due to vibrations. This led to screws coming loose and wires snapping. To fix this we used zipties to tie down our electronics. We also used tape to tape down screws and minimize the effects of vibrations.

While testing we also noticed that the gear ratio wasn't working well enough. To fix this we had to change the gear ratio froma. 1:1 to a 1:6. Though this seems like an easy change we discovered that the 64 tooth gear doesn't even fit because we drill pressed the hole for the motor shaft too low. To fix this issue, we cut in the bottom of the wood so the gear box's gears could spin freely.

We also ran into lots of issues with tnalged wires because the space inside was kind of cramped. To solve for this we first untnagled them, then we drilled holes in the bottom plate of the wood and used zip ties to keep them untangled.

Implementation and Final Product

Robotics PWM Motor Control.mov

This is a video of our code and how it worked on the motor. We programmed the arduino such that as you moved the controller's joystick up and down, the wheel turned clockwise and counterclockwise, respectively.

IMG_3476.MOV

Minibot Going Through the Obstacle Course

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