New Soft Robots Use Electropermanent (EP) Magnet Valves and Hydrogen Peroxide "Pneumatic Battery"

New Soft Robot Uses Electropermanent (EP) Magnet Valves and a Pneumatic Battery

I would like to introduce you to a new "elastomeric rolling robot" -- a soft robot made of inflatable, silicone actuators that pressurize in sequence to make the robot move.  This new robot hails from MIT's Distributed Robotics Laboratory and has a major distinguishing feature compared to other soft robots: it is entirely self-contained -- no more off-board electronics or pneumatics; everything is on-board. Two technologies facilitated this new robot:  (1) A "pneumatic battery" that uses mechanical feedback to self-regulate a chemical (hydrogen peroxide) reaction and maintain a stable pressure inside the robot's on-board pressure vessel.  (2) An energy-efficient pneumatic valve design based on electropermanent magnets (one of my favorite topics!).  These two new technologies were just presented at recent robotics conferences (ISRR 2011 and IROS 2011).  Be sure to check out the video below.

 

Elastomeric Rolling Robot

 

I'm a big advocate of the (now expired?) DARPA Chembot program; it resulted in a number of cool robots and technologies previously covered on Hizook: inflatable silicone robots, amoeba-like whole-skin locomotion, and of course the jamming skin locomotion (and subsequent jamming end effector).

Inflatable Silicone Robot  Amoeba Robot  Particle Jamming Robot Locomotion  Particle Jamming Gripper

 

However, this new robot from MIT's Distributed Robotics Laboratory (DRL) has one major, distinguishing feature: the robot is entirely self-contained -- no more off-board electronics or pneumatics; everything is on-board.  The "elastomeric rolling robot" is a soft robot made of inflatable, silicone actuators that cause the robot to roll when pressurized in sequence, as shown in the video below:

 

A  sequence of screenshots from the video:

Soft Robot Using EP Magnets and Pneumatic Battery  Soft Robot Using EP Magnets and Pneumatic Battery  Soft Robot Using EP Magnets and Pneumatic Battery

Soft Robot Using EP Magnets and Pneumatic Battery  Soft Robot Using EP Magnets and Pneumatic Battery  Soft Robot Using EP Magnets and Pneumatic Battery

 

Two technologies facilitated this new robot:  (1) A "pneumatic battery" that uses mechanical feedback to self-regulate a chemical (hydrogen peroxide) reaction.  This battery maintains a stable pressure inside the robot's on-board pressure vessel.  (2) An energy-efficient valve based on electropermanent magnets that only consumes power when switching states (zero static power consumption), which is used to control the pressurization of individual elastomer actuators and make the robot move.

 

Pneumatic Battery

 

The pneumatic battery was recently presented at the 2011 International Symposium on Robotics Research (ISRR2011) in a paper entitled "Soft Mobile Robots with On-Board Chemical Pressure Generation" (PDF) by DRL postdoc Cagdas Onal along with colleagues Xin Chen, George Whitesides, and Daniela Rus.  The basic principle behind the battery is (perhaps) best explained by this figure and caption:

Pneumatic Battery for Soft Mobile Robots with On-Board Chemical Pressure Generation  Pneumatic Battery for Soft Mobile Robots with On-Board Chemical Pressure Generation

Pneumatic Battery for Soft Mobile Robots with On-Board Chemical Pressure Generation

Side-view sketches (top) and the prototype (bottom) of the self-regulating chemical pneumatic pump mechanism, using hydrogen peroxide (H2O2) as a fuel. A deflector on the left side of the vessel deforms with increasing pressure and completely seals off the catalyst pack (0.2mm silver, gray) from the solution at a tuned critical pressure (top right), effectively stopping the reaction. The gas is filtered through a hydrophobic membrane filter on the right side before the outlet.

 

Clever.  This lets you generate additional pressure "on demand" (only after expending some of the contained pressure to activate the actuators) and limit the rate of the chemical reaction.    That should help prevent excessive pressures, explosive decompression, and excessive heat build-up.

 

 

Electropermanent (EP) Magnet Valves

 

Electropermanent (EP) magnets are probably my favorite new (and simultaneously very old) technology right now -- I wrote about them extensively following Ara Knaian's PhD dissertation, and that article is probably my favorite Hizook article of all time (so go read it!).  Basically, an EP magnet is a programmable magnet, sort of like an electromagnet... Except that it does not require a continuous current to maintain it's state -- it only requires electrical power when switching, and thus has zero static power consumption. 

Believe it or not... I predicted EP magnet-based valves when I first read Ara's thesis (you can check my "idea notebook" if you don't believe me!).  But due to crazy-long, distracting dissertation work, those clever folks at MIT beat me to the punch. 

Oh well, their design is clever.  Here is a cross-section of the valve.

 

Electropermanent (EP) Magnet Valve

When the EP magnet is actuated, a small ferrous ball in the flux path is drawn to the magnet, opening the valve and allowing fluid / air to flow.  When the EP magnet is not actuated, the ball clogs the outlet port and prevents flow.  Simple, elegant, and low-power owing to the awesomeness of electropermanent magnets.

This valve design was presented two weeks ago at IROS 2011 in a paper entitled, "Soft Robot Actuators using Energy-Efficient Valves Controlled by Electropermanent Magnets" (PDF).  The lead-author was Andrew Marchese, and he was accompanied by coauthors Cagdas Onal and Daniela Rus.

 

Final Remarks

 

I had the pleasure of meeting the lead authors from these two papers, Cagdas Onal and Andrew Marchese (and briefly Prof. Rus), at IROS 2011 out in San Francisco just two weeks ago.  I was pretty slammed with PhD dissertation work the entire conference (I spent most of my time in the hotel room writing and working on defense slides -- but hey, I passed my defense the week after!), so I didn't get to speak with them as much as I would have liked.  However, I did get to play around with an earlier soft robot prototype that was there in person (photo courtesy of Evan Ackerman), complete with EP magnet valves.

Soft Robot Using EP Magnets and Pneumatic Battery

I also got to speak with Cagdas and Andrew about alternative valve designs (eg. an EP magnet axially embedded in the tube rather than transverse to it) and other EP magnet applications. It sounds like there could be some interesting future collaborations brewing.

Here are some additional videos of earlier (tethered) prototypes:

 

Comments

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