Sorting plastic with robotics (V4)
Hello to the community! My name is Bradford and I’ve arrived in Eindhoven for robotics research. The loose plan at the moment is to provide a framework for robotic of sorting plastics by material. It’s a huge goal and we’re still laying out the groundwork to take it step by step. I’ll provide updates in this thread as we go!
But first, some background:
The most common sorting method seen in industry uses compressed air to blast target objects out of a fast moving stream of waste. Check out an example here: https://youtu.be/zIPGUv35A5E?t=100
It’s incredibly impressive to watch and well suited to large scale plants. There are even versions that can do it with plastic that has already been shredded into 2 mm flakes! Machines commonly use near infrared sensors sensors to identify plastics, although some streams use standard cameras that may sort by color. These systems are also typically binary by design. Each machine can only sort the incoming stream into two groups as controlled by the machine operator. The cost and space required for these industrial sorters is significant, meaning they are not typically found outside of large facilities.
On the opposite end of the spectrum, manual labor is also typical for countries with lower wages. Humans all over the world sort through the trash of others and collect bottles and other recyclable materials. https://youtu.be/dxsJVaL5vLc?t=483
There’s also sorting options that utilize the differences in plastic densities. There’s some discussion on that here: https://davehakkens.nl/community/forums/topic/plastic-sorting-a-personal-project/
With robotic arms getting more common and processors becoming cheaper, we feel there’s potential for a robotic solution in between industrial pneumatic air blasting and manual sorting.
We want to advance to physical testing as soon as possible as I only have 3 months here in the Netherlands (Visas are complicated :P). That means the first step is choosing hardware! I’ve spent the past few days researching a huge variety of arms. Here are some quick thoughts:
SCARA vs Delta vs 6DOF:
These are the three most common robot types used for pick and place operations. 6DOF arms are the most common and are highly adaptable for different tasks. SCARAs are a little more specialized for picking up and placing, but tend to have more limited reach. Delta robots are typically known for their speed and resemblance to spiders. A more detailed breakdown is here: https://www.crossco.com/blog/6-axis-vs-scara-vs-delta-vs-collaborative-robot-cage-match
A few options that look ideal for this research:
Franka Emika Panda: Feature packed, safe to work around, and appears easy to interface with. ROS integration is huge as I have experience there.
Dobot M1: Reasonably priced and seems easy to interface with, but the company has had some troubles shipping working products and I have yet to find any evidence of someone using it in the wild.
Buying an industrial machine secondhand: Still diving into other robots that could fall under this option. The industrial options I’ve looked at so far are likely out of our price range if bought new. There’s a few websites I’ve looked at that specialize in secondhand sales through Europe.
This is a deep project and there’s still a ton of challenges moving forward! For instance:
Choosing a suitable gripper
Interfacing with a near infrared sensor
If you have some knowledge to offer or want to help, feel free to shoot me an email at [email protected]. Always open to suggestions or ideas.
I am glad you’re interested in the topic, We will be exploring the Raman effect for both 532nm and 785 nm, so in case photoluminescence on the visual could arise as an issue we have the 785 and we will also have a platform to study different plastics on different wavelengths.
As of benchmarking and driving the robot we have tested matoha system and hoping opensourcing their project could be of interest to them.
We strive to provide an OpenSource / low cost solution capable of classifying plastic, going with the PreciousPlastic spirit of enabling plastic recycling to everyone for free.
We are working on the first prototype and will upload more info as we get our first spectra, meanwhile we are looking at using the robot for some other cool stuff to boost plastic recycling.
In case someone wants to learn a lot about the supporting technology while we figure it out here are some links, just be warned there are some advanced optics and lots of hacking needed:
Some progress on the sensor development, I have finished with the design for optical components placing, now I’m finishing manufacturing and starting to build a clean room, that is required for optics handling (Final prototype should consider a dust tight case). I will start a new forum thread as soon as I get some Spectra.
On the Robot side of things Brad has achieved improvements in object segmentation, path planning and functional demo. He is now preparing git repo and video documentation.
More coming soon!!
Thank you for the update. If you made a schematic layout of your instrument, if you don’t mind posting it, it would be very helpful for following along.
I was curious, how does the sensitivity of the detectors you chose compare to the typical SLR used in the third link you posted. They were doing a transmission measurement and commented on needing the sensitivity. Do you expect the reflected signal Raman effect to also need the high sensitivity?
Just learned that my email notifications for this thread weren’t making it to my inbox! Oh no! Thanks to @alromh87 for staying on top of things.
Time for my update! I came back to the Netherlands for April and May to give the robot a vision system. Aaaaand, it’s currently working!
I have to leave again in two weeks and am working on a more in depth video that explains everything. Looking forward to sharing it!
And one more gif of behind the scenes
I’m curious if there was any success in building the Raman effect instrument.
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