This week I did a lot of research into part purchases with Maxine. I looked into the motors, and how to control the different parts of the mechanical system. We knew that we wanted 3 stepper motors to control the XY motion, some way of gripping, some way of rotating the gripper, and a way to control the Z motion (as mentioned last week). After research, we decided on a NEMA 17 with a A4988 stepper driver for ease of control. We already knew we were going to use a NEMA 17 from the tutorial we were following, but especially since, we are aiming to use the RPi as a controller, we wanted to make sure the controls were well documented. So it seems like the A4988 was the most viable option with quite some documentation. We then decided that we were going to need a servo motor for grip rotation, which seemed easy enough to determine, since we shouldn’t need to exceed 180 degrees. In terms of the gripper, since we need to ensure that we had enough force to clamp down on the resistor and enough friction to keep it there, we went with a claw liked design that we have seen a few times in our research. With just one servo, we can 3D print our grippers. This will also allow us to experiment with different designs if our initial idea doesn’t work out.

So with all of this, we ordered the steppers and the stepper drivers and took out an Arduino Uno. This allows us be able to begin testing whether or not the motors work, as we move on to RPi development. As we did our research we realized that one issue might be that an RPi cannot support the level of accuracy we aim to have in our system, due to it having an OS, which includes interrupts and such, which will mess with the PWM signals. If this does happen, we will revert back to using an Arduino as a controller for the motors, with the RPi communicating to the Arduino, probably serially.

In addition to the work we have been doing, we have also been working on our Design Review slides. This time, I will be presenting, so I have also been practicing.