I am now the happy owner of a fully functional robotic tentacle. I’m pleased. After a few iterations, some hair pulling, and some welcome help from programmer, hacker, and generally pleasant person: TQ, the Trefoil Tentacle is now waving around in disconcerting 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.
I got some video of the thing waving around, flexing, and doing a 360 yesterday:
There’s a quadruped design getting its internals injection cast in wax this week, and you should be seeing some progress soon. I’ve been making steady progress on setting up an automated system to work out the internal geometry of these mechanisms with Meredith Patterson, and am hoping to have something to show for it in a month. All in all, the world of soft robotics is looking pretty promising at the moment.