Mechanical

Design

Designing our CAD in SolidWorks

When we thought of the concept of our delivery robot, we knew we wanted to go with a two-wheel drive and steer system. We decided to go with a double-deck to allow our vehicle to have a smaller area to not take up too much floor space. The decks, mounts, brackets, and storage box are all made from laser-cut 1/8" aircraft plywood. This material was chosen for it's strength to weight ratio as well as its high compression allowing it to not burn while being cut. To balance our robot, we used a steel ball caster in the back to rest on.

Executing the Design

You can see here how we were able to stay close to our original design in our execution. We were able to mount our two DC brushed motors to our bottom deck and attached to our 70 mm wheels. We separated the two decks using 3" spacers with our top deck housing our storage container and full-sized breadboard. Not seen in this image is our L239N motor driver mounted underneath the bottom deck just in front of our ball caster.

Calculations

Sizing our Motors

These are the calculations we used to determine which motors we should order to drive our robot. The max torque that we needed was 0.89 N*m. We used this information to purchase the Pololu 20D DC brushed 12V motor with 195:1 gear box which produces 0.98 N*m of torque.

Designing our Cam

By using trigonometry and similar triangle calculations to the left, we were able to design the cam's length needed to open our container's lid. The cam needed to be able to fit in the box and rotate enough to open our lid 80 degrees. We were able to determine the length needed to be 43mm.