This week, I spent most of my time doing CAD on Solidworks or researching design options.
I first made considerations for our linear actuation system. Given the height requirement of our robot, I thought it would be best to use a linear motion kit and decided to use the following pulley system described here: https://docs.revrobotics.com/15mm/linear-motion-kit. The primary motivation behind this selection was that it was built to sustain a multi-level cascading height that could reach our height requirement of 3 ft. Furthermore, it is very mounting-friendly for other parts (such as our claw or drivetrain) and price-accessible. This is better than other alternatives that are often significantly more expensive or cannot meet our height requirement (most common problem). I assembled the CAD for this part by using the standard part library from the vendor. The process was time-consuming as I had to relearn how to assemble with CAD, but I believe that it was valuable experience to help me with CADing the remainder of my part of the project.
Linear slide system CAD render (based on https://docs.revrobotics.com/15mm/linear-motion-kit/three-stage-cascading-lift)
I also invested several hours into checking the viability of using a vacuum suction gripper, following feedback from a recent meeting to consider it. Using a vacuum suction gripper was a good idea because of the benefit of reducing room for error and for emulating current industry solutions of our idea (i.e. https://www.youtube.com/watch?v=zeKfvUVbO3g&t=4s&ab_channel=IAMRobotics). The main issues I was facing in my research were the following:
- Limited amount of information about the performance of diy suction gripper kits: Most vendors make claims about the performance (i.e. how much load the system can carry), so this was the only basis we could make a decision off of. I was unable to find much solid, unbiased research to support these numbers quantitatively aside from anecdotal videos of performance.
- Limited availability of diy suction gripper kits: Almost all diys I could find were using some version of a standardized suction gripper kit that seems to only be sold from Chinese vendors and with an estimated shipping time of 1 month out in early Nov. There was also a single vendor on Robotshop that sold a potentially promising suction gripper system that uses a syringe+servo system instead of an air pump. The description claimed to be able to have a load of 3oz (0.21lbs) which could potentially be too poor of a performance.
Overall, the vacuum suction idea ended up being too high risk given its limited availability, so we decided to safely abandon the idea in favor for a claw.
Currently, I plan to use a claw system that is similar to off-the-shelf standard grippers (such as https://www.robotshop.com/en/actobotics-perpendicular-standard-gripper-kit-b.html) that is powered by a servo. The reasonably priced off-the-shelf parts do not seem to meet our requirements for objects to grab (small size maximum grip size of 4in and unknown (but likely very light) weights. My current research seems to indicate that CADing and laser cutting the claw is likely the correct direction, so I will continue to look in this direction (i.e. https://imgur.com/gallery/LpyW3).
I believe I am on track as the design research I did was thorough in making sure the chosen designs meet our requirements and are reasonably priced. I will be finalizing the claw idea and expanding upon the electronic hardware evaluation done last week by early tomorrow (in time for the design presentation).