09.2 Project Prototype
Kinematic analysis:
The above figure shows the following parameters:
The position of the tip of the second slotted linkage in x and y
The velocity of the tip versus the crank angle
The acceleration of the tip versus the crank angle
For our kinematic analysis and motion analysis, we asked ChatGPT to help because the linkage system that we designed was more complex than the systems that we had learned in class.
Below is an animation of the motion with the crank being the input variable.
Physical Prototype:
This is our small-scale prototype of our robotic arm mechanism for our cat toy. It consists of 3d printed parts made of PLA and PETG as well as a steel shaft, laser-cut wood, and some twine.
The above figure will be the next iteration of our design with a more robust design. The linkages are thicker as well as us using better bearings, and slotted links as opposed to a collar design.
Iteration Documentation:
We first tried making the crank and couplers out of 3mm plywood. The parts came out flimsy, and we decided to change from wood to acrylic. The acrylic was sturdier; the piece we had was thicker. We planned out the model by using shafts to mimic the actual links. We had iterations of the model where we wanted to put springs in the links and under the sliders to try and create a “home position.” We experimented with different tolerances for each hole that included: pegs for bearings, sliders on the shaft, and holes in couplers connecting links and sliders.
As shown in the second physical prototype figure, we realized the structural instability of the parts of our first iteration. We also had access to more and better bearings, which can be seen as cylinders pinning the linkages together. We also decided that a slotted slider was a better design choice for stability and under repeated loads as opposed to the collar design we had in our first iteration. The collar design had too much friction in the motion, and the slider should allow for less loss of force through the cranking motion. We also designed a more steady base to hold everything, which we will mount onto our existing RC car that we designed for Build Assignment 2.
Future Plans:
Our next steps will be to integrate the electronics into the CAD so that we don’t need to control the motion of the linkages manually. We will also need to purchase a Bluetooth module so we can control the RC car remotely, rather than using the wired design that we are currently using. We also need to design the gear system, which will help the arm system move independently of the RC car.
Draft BOM: