I am now the grinning overlord of a fully functional robotic tentacle. I’m quite pleased. After a few iterations, some hair pulling, and some utterly excellent help from programmer, hacker, and generally awesome person TQ, the Trefoil Tentacle is now waving about in all its eerie undulating glory. You can find a whole set of high res images of it here.
The control scheme is pretty simple: a barebones visual interface in Processing sends signals to an Arduino. From there, it switches the low power signal to high power via a Darlington transistor. The transistor switches each of 3 solenoid valves on and off, providing air to each of the 3 bladders inside of the silicone tentacle. The valves operate on a really slow PWM, their duty cycle determining how much air makes it to each bladder. Since there’s a bleed I can control on the system, I don’t have to worry about pumping air both in and out. I just adjust how much time the valves spend on, and the tentacle does it’s routine. All of the code for the setup is here on Adafruit’s forum. Continue reading →
Last week I headed up to Viridis3d for some more hacking. We got some beautiful results using some vaccuum casting with the trefoil design, parts printed for both the internals and outer shell of the quadruped, and schemes for tempting new mechanisms. All in all it’s been really exciting seeing the progress. Also, I have some updates on controlling the trefoil tentacle with an arduino powered set of air solenoids.
One of the confounding factors in getting this flavor of robot moving predictably has been how difficult it is to control wall thickness and bubble inclusions when casting the final silicone pieces. Like almost every mold, you do the best you can, try to create a nice, sterile, well ordered universe, and hope. Although Dragon Skin has performed really well as a durable, flexible silicone, it has the nasty habit of trapping bubbles in inconvenient spots when curing. Many silicones have a thin, pancake syrup consistency when mixed, but Dragon Skin is much more like honey or molasses, meaning it’s really easy to trap bubbles in the mix while stirring and have them set in place when everything’s curing. A good solution for the problem is pulling them back out with a vacuum chamber. Continue reading →
I’ve finally gathered my wits after a whirlwind tour of Europe, starting at CCC, giving some talks and connecting up with potential collaborators, to Berlin to meet hackers I hadn’t seen in years, to Brussels to play with some material science experiments in impact resisting plastics. While at CCC I gave three talks, two lightning talks on digital fabrication and the strange world of news advertisement, and a 15 minute talk on the methodology and philosophy behind my soft robots. I’ll be uploading the short talks sometime soon, but for now please see my soft robots lecture after the jump. Continue reading →
I have lots of updates to share. First, there’s a new video of the latest tentacle prototype in action below the fold. Second, We’ve made some excellent progress on the method of manufacture, reliability, and repeatability of the designs we’re producing. It’s almost at the point where we need to figure out a good real-world experiment to test our ideas against. I’m currently torn between creating a grasper and something that walks. Jim and I have been working out ways of getting a self contained power source inside of a soft robot, and it seems like we might be able to use a canister of compressed gas to do everything from timing movements to articulating valves. I’m working out ways of integrating peristaltic pumps and timing mechanisms that will be simple to prototype… which is a pretty tall order. However, I think a combo of laser cut bits and creative molding can have this one solved. Continue reading →