Category: Status Reports

I spent the last two weeks overhauling the entire physical design of the gantry. I replaced the aluminum angles with aluminum extrusions, and used brackets with t-nuts to provide an easily adjustable yet sturdy frame. I made it so that the supporting rod now goes through two wheel attachments which slide across the rails instead of having the rod sit on the edge of the frame. The z-axis rack has been changed from a 3d-printed part to a lazer cut one in order to make sure that it is rigid and straight. I also abandoned the bearing wheels on the z-axis in favor of a 3d-printed guide slot. I replaced some parts of the conveyor belt in order to add tension, and was able to pull the belt taught. I also made a mount for the conveyor belt stepper and added the stepper and the timing belt onto the conveyor, so that the conveyor now moves with the stepper motor. In short, the physical components of the gantry are essentially finished.

Next week, I plan to try to get the depth information from the stereo camera and help work on all of the steps necessary for integrating the work done by my teammates. I am behind schedule but I believe we should get everything done in time.

Verification

For our testing, we will test the gantry’s ability to move with a certain granularity. We’ll move it a certain number of steps and measure its movement in order to determine what the distance corresponding to a step is. We’ll also be doing rigorous testing with multiple common trash/recyclable items such as bottles, cans, cardboard, jars, chip bags, etc. to ensure that the end-effector is able to handle a wide variety of materials and surfaces. We will also make sure to test objects with different weights to determine if it is able to lift objects up to 1 lb. We’ll also be testing the overall accuracy of the depth information (z-coordinate of the object) calculated from the stereo camera.

This week was spent working on getting the vacuum end-effector to work. After some testing and design changes, I was able to get the end-effector to the point where it is able to pick up all 4 types of recycling consistently. I still need to add a release mechanism, which should just be a solenoid which opens and closes a hole in the air flow. I’ve designed and 3d-printed a part that should fit onto the end of the z-axis rack. I’ve also started looking into the stereo camera and the repository that comes with it to get the depth map from the camera. I also spent some time this week ordering parts, including the belt for the conveyor belt, silicone tubing for the vacuum pump, and aluminum extrusions for the gantry. The current construction of the gantry’s frame is hypothetically sufficient, but there seems to be severe wobbling, so switching from aluminum angles to aluminum extrusion should hopefully solve the problem.

Next week, I hope to attach the vacuum pump and suction end-effector to the gantry, get the conveyor belt cloth attached, get the depth map from the camera, and if time allows replace the aluminum angles with aluminum extrusion. I am behind schedule but I am catching up to what was planned.

Most of the time spent this week was on expanding and reinforcing the gantry to compensate for the sag caused by scaling up the design of the 4xidraw. I was able to construct a large frame around the conveyor belt in order to provide a mount for the 4xidraw. I then had to redesign some of the parts of the 4xidraw so that there would be no sag; this involved making one of the rods slide along the frame so that it supported the end-effector. I was also able to print out the rack so that the rack-and-pinion z-axis movement was complete. I’ve also begun testing the vacuum pump with the suction cup. It seems to be able to pick up flat, non-porous objects like plastic consistently, however it does not work as well with porous materials like paper.

Next week I plan to start working on programming the xy movement and will hopefully finish a fleshed out design of the vacuum end-effector. I am slightly behind schedule as I didn’t anticipate the rebuilding of the gantry to take as long as it did.

The picture of the current gantry is shown below:

The bulk of the time this week was spent designing parts for the z-axis movement/end effector as well as working on making a functioning conveyor belt. I’ve created CAD models for the rack and pinion movement, and have started assembly of the parts. I received multiple parts that had been ordered, including the suction-cup attachment for the end effector, and after some testing, decided that it would be necessary to actively pull a vacuum instead of having just passive suction. After some research, I was able to find a way to pull a vacuum (with minimal noise so it doesn’t interfere with other demos) and have ordered the parts for the vacuum attachment. I’m currently working on designing the 3d printed parts that will attach the vacuum and the end effector to the rack and pinion system. Additionally, I was able to construct a frame for the conveyor belt out of 3d printed parts and aluminum (image of frame is shown below). Currently working on designing a basic belt that will be the surface that the trash will rest on.

I am currently a little behind schedule, as the switch to an actively-pulled vacuum requires additional design work. I’m planning on finalizing the design of the z-axis/end effector and working on the Arduino code for the gantry xy movement for the over the next week.